Conjugated polymer, and electron donating organic material, material for photovoltaic device and photovoltaic device using the conjugated polymer

ABSTRACT

The objective of the present invention is to provide a photovoltaic device which has high photoelectric conversion efficiency and an electron-donating organic material which comprises a conjugate polymer having a structure of a thieno[3,4-b′]thiophene skeleton with an alkoxycarbonyl group in which a specific alkyl group part is a straight chain alkyl group or an alkanoyl group in which the alkyl group part is a straight chain alkyl group and a benzo[1,2-b:4, 5-b′]dithiophene skeleton with a heteroaryl group.

TECHNICAL FIELD

This disclosure relates to a conjugated polymer, and an electrondonating organic material, a material for a photovoltaic device and aphotovoltaic device using the conjugated polymer.

BACKGROUND

Solar cells that provide an environment-friendly electric energy sourcehave drawn public attention as an effective energy source that can solveenergy problems that have currently become more and more serious. Atpresent, as a semiconductor material for use in photovoltaic devices forsolar cells, inorganic substances such as monocrystalline silicon,polycrystalline silicon, amorphous silicon, and a compoundsemiconductor, have been used. However, since the solar cell to beproduced by using inorganic semiconductors requires high costs, it hasnot been widely used for general household purposes. The main reason forthe high costs lies in that a process of manufacturing a semiconductorthin-film requires high temperature and vacuum conditions. For thisreason, organic solar cells have been investigated in which, as asemiconductor material expected to simplify the manufacturing process,an organic semiconductor and an organic dye such as a conjugated polymerand an organic crystal are used.

However, the largest problem with the organic solar cells using theconjugated polymer or the like is that its photoelectric conversionefficiency is low compared to conventional solar cells using inorganicsemiconductors, and these solar cells have not been put into practicaluse. The reasons that the photoelectric conversion efficiency of theorganic solar cells using the conventional conjugated polymer is low liein that the absorbing efficiency of solar light is low, in that a boundstate referred to as an exciton state in which electrons and holesgenerated by solar light are hardly separated is formed, and in thatsince a trap which captures carriers (electrons and holes) is easilyformed, generated carriers are easily captured by the trap, resulting inthe slow mobility of carriers.

At present, the conventional photoelectric conversion device based onthe organic semiconductors can be classified into a schottky-typestructure in which an electron donating organic material (p-type organicsemiconductor) and metal having a small work function are joined to eachother, and a hetero junction type structure in which an electronaccepting organic material (n-type organic semiconductor) and anelectron donating organic material (p-type organic semiconductor) arejoined to each other. These devices have a low photoelectric conversionefficiency since only the organic layer (only several molecular layer)of the joined portion contributes to photoelectric current generation,and the improvement thereof has been required.

As a method of improving the photoelectric conversion efficiency, thereis a method of employing a bulk hetero junction type structure in whichan electron accepting organic material (n-type organic semiconductor)and an electron donating organic material (p-type organic semiconductor)are mixed with each other to increase the junction surface contributingto the photoelectric conversion. In particular, a photoelectricconversion device of a bulk hetero junction type has been reported inwhich a conjugated polymer is used as the electron donating organicmaterial (p-type organic semiconductor), and a conductive polymer havingn-type semiconductor characteristics, fullerene such as C₆₀ or afullerene derivative, is used as the electron accepting organicmaterial.

By the way, to efficiently absorb radiating energy which covers a widerange of solar light spectra to improve the photoelectric conversionefficiency, an electron donating organic material with a narrow band gapis useful (for example, refer to E. Bundgaard and F. C. Krebs, “SolarEnergy Materials & Solar Cells”, Vol. 91, p. 954, 2007 and H. Zhou, L.Yang, and W. You, “Macromolecules”, Vol. 45, p. 607, 2012). It isreported that as such a narrow-band-gap electron donating organicmaterial, a copolymer formed by combining a thieno[3,4-b]thiopheneskeleton with a benzo[1,2-b:4,5-b′]dithiophene skeleton exhibitsparticularly excellent photovoltaic characteristics, and manyderivatives have been synthesized (for example, refer to WO 2011/011545A).

However, in conventional electron donating organic materials formed bycopolymerization of the thieno[3,4-b]thiophene skeleton and thebenzo[1,2-b:4,5-b′]dithiophene skeleton, sufficient conversionefficiency is not achieved since it is not possible to pursue narrowingof a band gap, high carrier mobility and compatibility with the electronaccepting material typified by the fullerene derivatives simultaneously.It could therefore be helpful to provide an electron donating organicmaterial which pursues narrowing of a band gap, high carrier mobilityand compatibility with the electron accepting material simultaneously byselecting an optimum substituent and side chain, and provide aphotovoltaic device having high photoelectric conversion efficiency.

SUMMARY

We investigated the substituents and side chains of the conjugatedpolymer composed of the thieno[3,4-b]thiophene skeleton and thebenzo[1,2-b:4,5-b′]dithiophene skeleton and, consequently, found astructure which improves performance of the electron donating materialand increases conversion efficiency of the photovoltaic device.

We thus provide a conjugated polymer having a structure represented byformula (1), an electron donating organic material, a material for aphotovoltaic device and a photovoltaic device using the conjugatedpolymer.

In formula (1), R¹ represents an alkoxycarbonyl group in which an alkylgroup part is a straight chain alkyl group or an alkanoyl group in whichan alkyl group part is a straight chain alkyl group, and these groupsmay be substituted as long as they maintain a straight chain structure.Each of R²s which may be the same or different represents an optionallysubstituted heteroaryl group. X represents a hydrogen atom or a halogenatom. n indicates a polymerization degree and represents an integer of 2or more and 1000 or less.

It is thus possible to provide a photovoltaic device having highphotoelectric conversion efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an aspect of a photovoltaic device.

FIG. 2 is a schematic view showing another aspect of a photovoltaicdevice.

FIG. 3 is a schematic view showing another aspect of a photovoltaicdevice.

FIG. 4 is a schematic view showing another aspect of a photovoltaicdevice.

FIG. 5 is a voltage-current density curve of Example 1 (ratio between adonor and an acceptor is 1:1).

DESCRIPTION OF REFERENCE SIGNS

1: Substrate

2: Positive electrode

3: Organic semiconductor layer

4: Negative electrode

5: Layer having an electron donating organic material

6: Layer having an electron accepting organic material

DETAILED DESCRIPTION

A conjugated polymer includes a structure represented by formula (1)

In the above-mentioned formula (1), R¹ represents an alkoxycarbonylgroup in which an alkyl group part is a straight chain alkyl group or analkanoyl group in which an alkyl group part is a straight chain alkylgroup, and these groups may be substituted as long as they maintain astraight chain structure. By arranging a substituent having a carbonylgroup at the 2-position of a thieno[3,4-b]thiophene skeleton, the HOMOlevel of the conjugated polymer can be deepened, and an open circuitvoltage of the photovoltaic device can be increased when the conjugatedpolymer is used as an electron donating organic semiconductor. Thestraight chain alkyl group can improve carrier mobility of theconjugated polymer since the straight chain alkyl group can enhance apacking property of a copolymer more than a branched alkyl group.

Each of R²s which may be the same or different represents an optionallysubstituted heteroaryl group. By introducing a heteroaryl group at aposition of R² of formula (1), planarity of the copolymer can beenhanced, and the carrier mobility of the conjugated polymer can beenhanced.

The alkoxycarbonyl group refers to an alkyl group with an ester bondinterposed. The alkanoyl groups refers to an alkyl group with a ketonegroup interposed.

Further, the straight chain alkyl group is a straight chain saturatedaliphatic hydrocarbon groups such as a propyl group, a butyl group, apentyl group, a hexyl group, a heptyl group, an octyl group, a nonylgroup, a decyl group, an undecyl group, and a dodecyl group, and thesemay be unsubstituted, or may be substituted as long as they maintain astraight chain structure. Moreover, the substituent may be furthersubstituted as long as it maintains a straight chain structure. Examplesof the substituent in substitutions while maintaining the straight chainstructure include an alkoxy group, a thioalkoxy group, and halogen. Thenumber of carbon atoms of the alkyl group is preferably 4 or more and 10or less, and particularly preferably 7 or more and 9 or less to pursuesufficient solubility and carrier mobility of the conjugated polymersimultaneously. Halogen as the substituent on the alkyl group has theeffect of improving an agglomerated state of the conjugated polymer, andfluorine with a small atomic radius is preferably used.

The heteroaryl group represents an aromatic heterocyclic group having anatom other than carbon atoms such as a thienyl group, a furyl group, apyrrolyl group, an imidazolyl group, a pyrazolyl group, an oxazolylgroup, a pyridyl group, a pyrazyl group, a pyrimidyl group, or athienothienyl group. The number of carbon atoms of the heteroaryl groupused for R² is preferably 2 or more and 6 or less for maintaining thecarrier mobility, and the thienyl group or the furyl group which has afive-membered ring structure with a small molecular size is particularlypreferably used to suppress a twist from the benzodithiophene skeletonto enhance the packing property. As the substituent on the heteroarylgroup, alkyl groups or alkoxy groups having 6 to 10 carbon atoms ispreferred in order to pursue the solubility and carrier mobility of theconjugated polymer simultaneously, and these groups may be straight orbranched.

In formula (1), X represents a hydrogen atom or a halogen atom. Halogenrefers to any one of fluorine, chlorine, bromine and iodine. A fluorineelement having a small atomic radius is particularly preferably used toeffectively deepen the HOMO level of the conjugated polymer and also tomaintain the packing property.

Further, n indicates a polymerization degree and represents an integerof 2 or more and 1000 or less. When n is set to 5 or more, the carriermobility of the conjugated polymer can be increased, and an effectivecarrier path can be formed in a thin film of the above-mentioned bulkhetero junction type and, therefore, the photoelectric conversionefficiency can be increased. n is preferably less than 100 from theviewpoint of ease of synthesis. The polymerization degree can bedetermined from the weight-average molecular weight. The weight-averagemolecular weight can be determined by measuring by use of GPC (gelpermeation chromatography), and converting the measurement to thepolystyrene standard-sample basis. In addition, thethieno[3,4-b]thiophene skeleton may be directed at random orregioregularly in the conjugated polymer.

Many characteristics such as the narrow band gap, the high carriermobility, the solubility in an organic solvent and the compatibilitywith the electron accepting material typified by the fullerenederivatives are required of the electron donating organic material inthe above-mentioned photovoltaic device of a bulk hetero junction type.The conjugated polymer having a structure represented by formula (1),which is formed by arranging a specific substituent and side chain in aconjugated polymer composed of a thieno[3,4-b]thiophene skeleton and abenzo[1,2-b:4,5-b′]dithiophene skeleton, can satisfy all thesecharacteristics, and the conjugated polymer can be preferably used as anelectron donating organic material in the photovoltaic device of thebulk hetero junction type.

Specific examples of the conjugated polymer having the structurerepresented by formula (1) include following structures. n represents aninteger of 2 or more and 1000 or less.

Moreover, in the conjugated polymer having a structure represented byformula (1), the structure represented by formula (1) may be acombination of structures in which R¹s, R²s and Xs are different as longas the structures respectively satisfy a structure represented byformula (1). Examples thereof include the following structures. Anumeral subscript of a repeating unit in parentheses represents a ratioof the repeating unit. n represents an integer of 2 or more and 1000 orless.

Moreover, the conjugated polymer having a structure represented byformula (1) may be a copolymer further containing a divalent conjugatedlinking group. The amount of the divalent conjugated linking group ispreferably 20% by weight or less with respect to the entire conjugatedpolymer for maintaining the carrier mobility of the conjugated polymer.The amount of the divalent conjugated linking group is more preferably10% by weight or less.

Examples of a preferred divalent conjugated linking group include thefollowing structure. Among these, a structure composed of thethieno[3,4-b]thiophene skeleton and the benzo[1,2-b:4,5-b′]dithiopheneskeleton is preferred for maintaining the carrier mobility of theconjugated polymer.

Each of R³ to R⁵³ which may be the same or different is selected fromamong hydrogen, an alkyl group, an alkoxy group, an alkoxycarbonylgroup, an alkylthioester group, an alkanoyl group, an aryl group, aheteroaryl group, and halogen.

In addition, the conjugated polymer having a structure represented byformula (1) can be synthesized, for example, by a method similar thatdescribed in WO 2011/011545 A described above, or a method similar thatdescribed in Y. Liang, D. Feng, Y. Wu, S.-T. Tsai, G. Li, C. Ray, L. Yu,“Journal of the American Chemical Society”, Vol. 131, p. 7792, 2009, orF. He, W. Wang, W. Chen, T. Xu, S. B. Darling, J. Strzalka, Y. Liu, L.Yu, “Journal of the American Chemical Society”, Vol. 133, p. 3284, 2011.

The material for a photovoltaic device may be composed of only theelectron donating organic material using the conjugated polymer having astructure represented by formula (1), or may contain another electrondonating organic material. Examples of other electron donating organicmaterials include conjugated polymers, such as a polythiophene polymer,benzothiadiazole-thiophene derivatives, a benzothiadiazole-thiophenecopolymer, a poly(p-phenylenevinylene)polymer, apoly(p-phenylene)polymer, a polyfluorene polymer, a polypyrrole polymer,a polyaniline polymer, a polyacetylene polymer, and a poly(thienylenevinylene)polymer; and low-molecular weight organic compounds includingphthalocyanine derivatives, such as H₂ phthalocyanine (H₂Pc), copperphthalocyanine (CuPc) and zinc phthalocyanine (ZnPc); porphyrinderivatives; triaryl amine derivatives, such asN,N′-diphenyl-N,N′-di(3-methylphenyl)-4,4′-diphenyl-1,1′-diamine (TPD)and N,N′-dinaphtyl-N,N′-diphenyl-4,4′-diphenyl-1,1′-diamine (NPD);carbazole derivatives, such as 4,4′-di(carbazole-9-yl)biphenyl (CBP);and oligothiophene derivatives (terthiophene, quaterthiophene,sexithiophene, octithiophene and the like).

The conjugated polymer having a structure represented by formula (1) isan electron donating organic material exhibiting p-type organicsemiconductor characteristics, and in the material for a photovoltaicdevice, the electron donating organic material is preferably combinedwith the electron accepting organic material (n-type organicsemiconductor) in order to obtain higher photoelectric conversionefficiency.

Examples of the electron accepting organic material which exhibits ann-type semiconductor characteristic include: oxazole derivatives such as1,4,5,8-naphthalene tetracarboxylic dianhydride (NTCDA),3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA),3,4,9,10-perylenetetracarboxylic bisbenzimidazole (PTCBI),N,N′-dioctyl-3,4,9,10-naphthyltetracarboxy diimide (PTCDI-C8H),2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD), and2,5-di(1-naphthyl)-1,3,4-oxadiazole (BND); triazole derivatives such as3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole (TAZ);phenanthroline derivatives, phosphine oxide derivatives, fullerenecompounds (unsubstituted compounds including C₆₀, C₇₀, C₇₆, C₇₈, C₈₂,C₈₄, C₉₀ and C₉₄, [6,6]-phenyl C61 butyric acid methylester([6,6]-PCBM), [5,6]-phenyl C61 butyric acid methylester ([5,6]-PCBM),[6,6]-phenyl C61 butyric acid hexylester ([6,6]-PCBH), [6,6]-phenyl C61butyric acid dodecylester ([6,6]-PCBD), phenyl C71 butyric acidmethylester (PC₇₀BM), and phenyl C85 butyric acid methylester (PC₈₄BM)),carbon nanotubes (CNT), and a derivative prepared by introducing a cyanogroup to a poly-p-phenylenevinylene polymer (CN-PPV). Among these, thefullerene compound is preferably used since it has high chargeseparating rate and electron transfer rate. Among the fullerenecompounds, the C₇₀ derivative (the above-mentioned PC₇₀BM or the like)is more preferably used since it is excellent in a light absorbingcharacteristic, and provides a higher photoelectric conversionefficiency.

In the material for a photovoltaic device, in which the electrondonating organic material using the conjugated polymer having astructure represented by formula (1) is combined with the electronaccepting organic material, the content ratio (weight percentage)between the electron donating organic material and the electronaccepting organic material is not particularly limited; however, thecontent ratio between the electron donating organic material and theelectron accepting organic material (ratio between a donor and anacceptor) is preferably 1:99 to 99:1, more preferably 10:90 to 90:10,and moreover preferably 20:80 to 60:40.

The electron donating organic material and the electron acceptingorganic material may be mixed for use, or may be stacked for use. Amethod of mixing the materials is not particularly limited, and examplesthereof include a method in which these materials are added to a solventat a desired ratio, and then dissolved in the solvent by one or acombination of plural process such as heating, stirring and irradiationwith ultrasonic waves. In addition, when the material for a photovoltaicdevice forms a single organic semiconductor layer, as described later,the above-mentioned content ratio refers to a content ratio between theelectron donating organic material and the electron accepting organicmaterial contained in the single layer, and when the organicsemiconductor layer has a stacked structure having two or more layers,the above-mentioned content ratio refers to a content ratio between theelectron donating organic material and the electron accepting organicmaterial in the entire organic semiconductor layers.

To further improve the photoelectric conversion efficiency, it ispreferred to eliminate, as far as possible, impurities which might causea trap of carriers. A method of removing impurities in the electrondonating organic material using the conjugated polymer having astructure represented by formula (1) or the electron accepting organicmaterial is not particularly limited, and the following methods may beused: a column chromatography method, a re-crystallizing method, asublimation method, a re-precipitation method, a Soxhlet extractionmethod, a molecular weight fractionation method by using GPC, afiltration method, an ion exchange method, a chelate method, and thelike. In general, a column chromatography method, a re-crystallizingmethod, or a sublimation method is preferably used for refining alow-molecular weight organic material. On the other hand, to refine ahigh-molecular weight organic material, a re-precipitation method, aSoxhlet extraction method, a molecular weight fractionation method byusing GPC, or a filtration method is preferably used when alow-molecular weight component is eliminated, and a re-precipitationmethod, a chelate method, or an ion exchange method is preferably usedwhen a metal component is eliminated. Among these methods, a pluralityof methods may be combined.

Next, the photovoltaic device will be described. The photovoltaic devicehas at least a positive electrode and a negative electrode, and containsthe material for a photovoltaic device between the positive electrodeand the negative electrode. FIG. 1 is a schematic view showing anexample of a photovoltaic device. In FIG. 1, reference numeral 1represents a substrate, reference numeral 2 represents the positiveelectrode, reference numeral 3 represents an organic semiconductor layercontaining the material for a photovoltaic device, and reference numeral4 represents the negative electrode. The photovoltaic device may bestacked in order of substrate 1/negative electrode 4/organicsemiconductor layer 3/positive electrode 2, as shown in FIG. 2.

The organic semiconductor layer 3 contains the material for aphotovoltaic device. That is, the organic semiconductor layer 3 containsthe electron donating organic material using the conjugated polymerhaving a structure represented by formula (1) and the electron acceptingorganic material. When the organic semiconductor layer 3 serving as anorganic power generating layer of the photovoltaic device contains theelectron donating organic material and the electron accepting organicmaterial, these materials may be mixed with each other, or formed asstacked layers. However, the mixed state is preferred. That is, theorganic semiconductor layer containing the material for a photovoltaicdevice may be a layer in which the electron donating organic materialand the electron accepting organic material are mixed, as shown in FIGS.1 and 2, or the organic semiconductor layer containing the material fora photovoltaic device may have a stacked structure of a layer containingthe electron donating organic material and a layer containing theelectron accepting organic material, as shown in FIGS. 3 and 4. However,the organic semiconductor layer containing the material for aphotovoltaic device is preferably a layer in which the electron donatingorganic material and the electron accepting organic material are mixed.

The photovoltaic device of the bulk hetero junction type is preferred,in which the area of the junction between the electron donating organicmaterial and the electron accepting organic material, contributing tothe photoelectric conversion, is increased by mixing the electrondonating organic material and the electron accepting organic material.In the organic semiconductor layer 3 which is the organic powergenerating layer of the bulk hetero junction type, the electron donatingorganic material using the conjugated polymer having a structurerepresented by formula (1) and the electron accepting organic materialare phase-separated from each other in a level of a nanometer. A size ofa domain of the phase-separation structure is not particularly limited.However, it is usually 1 nm or more and 50 nm or less.

Further, when the electron donating organic material using theconjugated polymer having a structure represented by formula (1) isstacked on the electron accepting organic material, it is preferred thatthe layer containing the electron donating organic material exhibiting ap-type semiconductor characteristic is placed on the positive electrodeside, and the layer containing the electron accepting organic materialexhibiting an n-type semiconductor characteristic is placed on thenegative electrode side. FIGS. 3 and 4 illustrate one example of thephotovoltaic device when the organic semiconductor layer 3 is stacked inthis way. Reference numeral 5 represents a layer having the electrondonating organic material using the conjugated polymer having astructure represented by formula (1), and reference numeral 6 representsa layer having the electron accepting organic material. The organicsemiconductor layer preferably has a thickness of 5 nm to 500 nm, andmore preferably a thickness of 30 nm to 300 nm. The layer having theelectron donating organic material preferably has a thickness of 1 nm to400 nm of the thickness of the organic semiconductor layer, morepreferably a thickness of 15 nm to 150 nm.

In the photovoltaic device, either the positive electrode 2 or thenegative electrode 4 preferably has a light-transmitting property. Thelight-transmitting property of the electrode is not particularly limitedas long as it allows incident light to reach the organic semiconductorlayer 3 so that an electromotive force is generated. Herein, thelight-transmitting property is a value obtained by the followingexpression:[Transmitted light intensity (W/m²)/Incident light intensity(W/m²)]×100(%).The thickness of the electrode is only necessary to be in such a rangethat provides a light-transmitting property and conductivity, andalthough different depending on the electrode materials, it ispreferably 20 nm to 300 nm. In addition, a light-transmitting propertyis not necessarily required of the other electrode as long as theconductivity is provided, and the thickness of the other electrode isalso not particularly limited.

Examples of a material preferably used as an electrode material includemetals such as gold, platinum, silver, copper, iron, zinc, tin,aluminum, indium, chromium, nickel, cobalt, scandium, vanadium, yttrium,indium, cerium, samarium, europium, terbium, and ytterbium; oxides ofmetals such as indium, tin, molybdenum and nickel; composite metaloxides (indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zincoxide (AZO), gallium zinc oxide (GZO) and the like); alkali metals andalkaline-earth metals, specifically, lithium, magnesium, sodium,potassium, calcium, strontium and barium. Moreover, electrodes composedof alloys made from the above-mentioned metals or laminates of theabove-mentioned metals are also preferably used. An electrode containinggraphite, a graphite intercalation compound, a carbon nanotube,graphene, polyaniline or its derivatives, or polythiophene or itsderivatives is also preferably used. In this case, it is preferred thatat least one of the positive electrode and the negative electrode istransparent or translucent. The above-mentioned electrode material mayform a mixed layer or a stacked structure, which are respectively madefrom two or more materials.

The conductive material to be used for the positive electrode 2 ispreferably a compound to be ohmic-joined to the organic semiconductorlayer 3. Moreover, when a hole transporting layer described later isused, the conductive material to be used for the positive electrode 2 ispreferably a compound to be ohmic jointed to the hole transportinglayer. The conductive material to be used for the negative electrode 4is preferably a compound to be ohmic-joined to the organic semiconductorlayer 3 or an electron transporting layer. Examples of a method ofimproving joining include a method in which metal fluoride such aslithium fluoride (LiF) and cesium fluoride is introduced into thenegative electrode as an electron extraction layer. Introduction of theelectron extraction layer allows an extraction current to improve.

Depending on the kinds and usages of the photoelectric conversionmaterial, the substrate 1 may be formed as a substrate on which anelectrode material and an organic semiconductor layer can be stacked,for example, as a film or a plate prepared by using any method from aninorganic material such as non-alkali glass, quartz glass, aluminum,iron, copper or an alloy such as stainless steel, or an organic materialsuch as polyester, polycarbonate, polyolefin, polyamide, polyimide,polyphenylene sulfide, polyparaxylene-polymethyl methacrylate, an epoxyresin, or a fluorine-based resin. Further, when incident light from thesubstrate side is used, it is preferred that each of the above-mentionedsubstrates preferably has a light-transmitting property of 80% or more.

The hole transporting layer may be disposed between the positiveelectrode 2 and the organic semiconductor layer 3. Examples of amaterial to form the hole transporting layer preferably includeconductive polymers such as a polythiophene-based polymer, apoly-p-phenylenevinylene-based polymer, a polyfluorene-based polymer, apolypyrrole polymer, a polyaniline polymer, a polyfuran polymer, apolypyridine polymer, and a polycarbazole polymer; low-molecular weightorganic compounds exhibiting p-type semiconductor characteristics suchas phthalocyanine derivatives (H₂Pc, CuPc, ZnPc and the like), porphyrinderivatives, and acene-based compounds (tetracene, pentacene and thelike); carbon compounds such as graphene and graphene oxide; andinorganic compounds including molybdenum oxide (MoO_(x)) such as MoO₃,tungsten oxide (WO_(x)) such as WO₃, nickel oxide (NiO)_(x) such as NiO,vanadium oxide (VO_(x)) such as V₂O₅, zirconium oxide (ZrO_(x)) such asZrO₂, copper oxide (CuO_(x)) such as Cu₂O, copper iodide, rutheniumoxide (RuO_(x)) such as RuO₄, and ruthenium oxide (ReO_(x)) such asRe₂O₇. Particularly, polyethylene dioxythiophene (PEDOT) serving as apolythiophene-based polymer, those materials prepared by addingpolystyrene sulfonate (PSS) to PEDOT, molybdenum oxide, vanadium oxideand tungsten oxide, are preferably used. The hole transporting layer maybe a layer made of a single compound, or may be a mixed layer or astacked structure, which are respectively made of two or more compounds.Moreover, the hole transporting layer preferably has a thickness of 5 to600 nm, more preferably a thickness of 10 to 200 nm.

Moreover, in the photovoltaic device, the electron transporting layermay be disposed between the organic semiconductor layer 3 and thenegative electrode 4. The material used to form the electrontransporting layer is not particularly limited, and examples of thematerial preferably used include organic materials exhibiting n-typesemiconductor characteristics such as the above-mentioned electronaccepting organic materials (NTCDA, PTCDA, PTCDI-C8H, oxazolederivatives, triazole derivatives, phenanthroline derivatives, phosphineoxide derivatives, phosphine sulfide derivatives, quinoline derivatives,fullerene compounds, CNT, CN-PPV and the like). Further, ioniccompounds, such as an ionic substituted fluorene polymer (“AdvancedMaterials”, Vol. 23, pp. 4636-4643, 2011, “Organic Electronics”, Vol.10, pp. 496-500, 2009) and a combination of the ionic substitutedfluorene polymer and a substituted thiophene polymer (“Journal ofAmerican Chemical Society”, Vol. 133, pp. 8416-8419, 2011), polyethyleneoxide (“Advanced Materials”, Vol. 19, pp. 1835-1838, 2007) and the likecan also be used as the electron transporting layer.

Moreover, compounds having ionic groups such as ammonium salt, aminesalt, pyridinium salt, imidazolium salt, phosphonium salt, carboxylatesalt, sulfonate salt, phosphate salt, sulfuric acid ester salt,phosphoric acid ester salt, sulfate salt, nitrate salt, acetonate salt,oxo acid salt and a metal complex, can also be used as the electrontransporting layer. Specific examples thereof include ammonium chloride,ammonium acetate, ammonium phosphate, hexyltrimethylammonium bromide,tetrabutylammonium bromide, octadecyltrimethylammonium bromide,hexadecylpyridinium bromide, 1-butyl-3-methylimidazolium bromide,tributylhexadecylphosphonium bromide, zinc formate, zinc acetate, zincpropionate, zinc butyrate, zinc oxalate, sodium heptadecafluorononanate,sodium myristate, sodium benzoate, sodium 1-hexadecanesulfonate, sodiumdodecyl sulfate, sodium monododecyl phosphate, zinc acetylacetonate,ammonium chromate, ammonium metavanadate, ammonium molybdate, ammoniumhexafluorozirconate, sodium tungstate, ammonium tetrachlorozincate,tetraisopropyl orthotitanate, lithium nickelate, potassium permanganate,silver phenanthroline complex, AgTCNQ, and compounds used for theelectron transporting layer, which is described in Japanese PatentLaid-open Publication No. 2013-58714.

Also, inorganic materials, for example, metal oxides including titaniumoxide (TiO_(x)) such as TiO₂, zinc oxide (ZnO_(x)) such as ZnO, siliconoxide (SiO_(x)) such as SiO₂, tin oxide (SnO_(x)) such as SnO₂, tungstenoxide (WO_(x)) such as WO₃, tantalum oxide (TaO_(x)) such as Ta₂O₃,barium titanate (BaTi_(x)O_(y)) such as BaTiO₃, barium zirconate(BaZr_(x)O_(y)) such as BaZrO₃, zirconium oxide (ZrO_(x)) such as ZrO₂,hafnium oxide (HfO_(x)) such as HfO₂, aluminum oxide (AlO_(x)) such asAl₂O₃, yttrium oxide (YO_(x)) such as Y₂O₃ and zirconium silicate(ZrSi_(x)O_(y)) such as ZrSiO₄; nitrides including silicon nitride(SiN_(x)) such as Si₃N₄; and semiconductors including cadmium sulfide(CdS_(x)) such as CdS, zinc selenide (ZnSe_(x)) such as ZnSe, zincsulfide (ZnS_(x)) such as ZnS, and cadmium telluride (CdTe_(x)) such asCdTe, are preferably used as the electron transporting layer.

Examples of a method of forming the electron transporting layer by usingthe above-mentioned inorganic material include a method in which asolution of a precursor of metal salt or metal alkoxide of the inorganicmaterial is applied and then heated to form a layer, and a method offorming a layer by applying a dispersion of nanoparticles onto asubstrate. Depending on a heating temperature and time and a synthesiscondition of nanoparticles, a reaction does not have to proceedcompletely, and the precursor may be partially hydrolyzed or partiallycondensed to become an intermediate product or become a mixture of theprecursor, the intermediate product and a final product.

The phenanthroline derivative is not particularly limited, and examplesthereof include phenanthroline monomer compounds such as bathocuproine(BCP), bathophenanthroline (Bphen),2-(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (HNBphen), and2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (NBphen); andphenanthroline oligomer compounds described in Japanese Patent Laid-openPublication No. 2012-39097. The phenanthroline dimer compound is asdescribed in Japanese Patent Laid-open Publication No. 2012-39097, andis compounds represented by formula (2).

Each of R⁵⁴ to R⁶⁰ which may be the same or different is selected fromamong hydrogen, an alkyl group, and an aryl group. A represents adivalent aromatic hydrocarbon group. Two substituents having aphenanthroline skeleton may be the same or different. The alkyl groupindicates saturated aliphatic hydrocarbon groups such as a methyl group,an ethyl group, a propyl group, and a butyl group, and the aryl groupindicates aromatic hydrocarbon groups such as a phenyl group, a tolylgroup, a biphenyl group, a naphthyl group, a phenanthryl group, and ananthryl group, and these groups may be unsubstituted, or may besubstituted. The number of carbon atoms of the alkyl group or aryl groupis preferably about 1 to 20. Two groups having a phenanthroline skeletonmay be the same or different.

The above-mentioned phosphine oxide derivative is not particularlylimited, and examples thereof include phosphine compounds such asphenyl-dipyrenylphosphine oxide (POPy₂).

The above-mentioned quinoline derivative is not particularly limited,and examples thereof include compounds such as lithium8-hydroxyquinolate (Liq) and aluminum tris(8-hydroxyquinolate).

A mechanism in which the characteristic is improved by these electrontransporting layers is not apparent. However, it is considered that theelectron extraction efficiency and charge generation efficiency areimproved by the actions that the electron transporting layer reducesenergy barrier in a joint interface to the negative electrode, and thatthe electron transporting layer prevents deactivation of excitonsgenerated in the electron donating organic semiconductor and theelectron accepting organic semiconductor at the interface with thenegative electrode.

Among the above-mentioned electron transporting layers, thephenanthroline derivative is preferably used since it has an electrontransporting property and facilitates obtaining a uniform film.Moreover, the phenanthroline oligomer compound is preferably used sinceit facilitates obtaining a stable film having a high glass transitionpoint, and the phenanthroline dimer compound is furthermore preferablyused in consideration of ease of synthesis. Among the phenanthrolinedimer compounds, a phenanthroline dimer compound in which A in formula(2) is a substituted or unsubstituted phenylene group or a substitutedor unsubstituted naphthylene group is preferably used because of abalance between a sublimating property at the time of forming a thinfilm such as the time of vacuum vapor deposition and an ability to forma thin-film.

The electron transporting layer preferably has a thickness of 0.1 to 600nm, more preferably a thickness of 1 to 200 nm, and moreover preferablya thickness of 1 to 20 nm. The electron transporting layer may be alayer made of a single compound, or may be a layer made of two or morecompounds. Moreover, the electron transporting layer may be a mixedlayer of an alkali metal or an alkaline-earth metal, specificallylithium, magnesium, calcium, or compounds including metal fluoride suchas lithium fluoride and cesium fluoride, and the above-mentionedmaterial for the electron transporting layer, or may be a stackedstructure thereof.

Moreover, in the photovoltaic device, two or more organic semiconductorlayers may be stacked with one or more intermediate electrodesinterposed there between to form series junctions. Such a constitutionis sometimes referred to as a tandem structure. For example, the tandemstructure includes: substrate/positive electrode/first organicsemiconductor layer/intermediate electrode/second organic semiconductorlayer/negative electrode. Another tandem structure includes:substrate/negative electrode/first organic semiconductorlayer/intermediate electrode/second organic semiconductor layer/positiveelectrode. By using this tandem structure, it becomes possible toimprove an open circuit voltage. In addition, the above-mentioned holetransporting layer may be disposed between the positive electrode andthe first organic semiconductor layer, and between the intermediateelectrode and the second organic semiconductor layer, and the holetransporting layer may be disposed between the first organicsemiconductor layer and the intermediate electrode, and between thesecond organic semiconductor layer and the negative electrode.

When such a tandem structure is employed, it is preferred that at leastone layer of organic semiconductor layers contains the material for aphotovoltaic device and another layer contains an electron donatingorganic material different in a band gap from the electron donatingorganic material using the conjugated polymer having a structurerepresented by formula (1) to avoid a reduction of the short-circuitcurrent. Examples of such an electron donating organic materials includeconjugated polymers such as a polythiophene polymer, apoly(p-phenylenevinylene)polymer, a poly(p-phenylene)polymer, apolyfluorene polymer, a polypyrrole polymer, a polyaniline polymer, apolyacetylene polymer, a poly(thienylene vinylene)polymer, and abenzothiadiazole polymer (e.g., PCPDTBT(poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)]), and PSBTBT(poly[(4,4-bis-(2-ethylhexyl)dithieno[3,2-b:2′,3′-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl]));and the low-molecular weight organic compounds including phthalocyaninederivatives such as H₂ phthalocyanine (H₂Pc), copper phthalocyanine(CuPc) and zinc phthalocyanine (ZnPc); porphyrin derivatives; triarylamine derivatives such asN,N′-diphenyl-N,N′-di(3-methylphenyl)-4,4′-diphenyl-1,1′-diamine (TPD)and N,N′-dinaphtyl-N,N′-diphenyl-4,4′-diphenyl-1,1′-diamine (NPD);carbazole derivatives such as 4,4′-di(carbazole-9-yl)biphenyl (CBP); andoligothiophene derivatives (terthiophene, quaterthiophene,sexithiophene, octithiophene and the like).

Moreover, as a material for the intermediate electrode to be usedherein, those having high conductivity are preferably used, and examplesthereof include the above-mentioned metals such as gold, platinum,chromium, nickel, lithium, magnesium, calcium, tin, silver and aluminum;oxides of metals such as indium, tin and molybdenum having transparency;and composite metal oxides (indium tin oxide (ITO) and indium zinc oxide(IZO) and the like); alloys made from the above-mentioned metals andlaminates of the above-mentioned metals; and polyethylene dioxythiophene(PEDOT) and PEDOT to which polystyrene sulfonate (PSS) is added. Theintermediate electrode preferably has a light-transmitting property, andeven in the case of a material such as metal having a lowlight-transmitting property, by making the film thickness thinner, asufficient light-transmitting property can be ensured in many cases.

Next, a method of producing a photovoltaic device will be described byway of examples. A transparent electrode (in this case, corresponding toa positive electrode) such as ITO is formed on a substrate by asputtering method or the like. A material for a photovoltaic device,which contains an electron donating organic material using theconjugated polymer having a structure represented by formula (1), and anelectron accepting organic material as required, is dissolved in asolvent to prepare a solution, and the solution is applied onto thetransparent electrode to form an organic semiconductor layer.

The solvent to be used in this time is not particularly limited as longas it allows the organic semiconductor to be appropriately dissolved ordispersed in a solvent. However, an organic solvent is preferred, andexamples of the organic solvent include aliphatic hydrocarbons such ashexane, heptane, octane, isooctane, nonane, decane, cyclohexane, decalinand bicyclohexyl; alcohols such as methanol, ethanol, butanol, propanol,ethylene glycol and glycerin; ketones such as acetone, methyl ethylketone, cyclopentanone, cyclohexanone and isophorone; esters such asethyl acetate, butyl acetate, methyl lactate, γ-butyrolactone,diethylene glycol monobutyl ether acetate and dimethyl carbonate; etherssuch as ethyl ether, methyl tert-butyl ether, tetrahydrofuran,1,4-dioxane, tetrahydropyran, 3,4-dihydro-2H-pyran, isochroman, ethyleneglycol monomethyl ether and diglyme; amines such as ammonia and ethanolamine; amides such as N,N-dimethylformamide, dimethylacetamide andN-methyl-2-pyrrolidone; sulfones such as sulfolane; sulfoxides such asdimethyl sulfoxide; carbon disulfide; thiols such as 1,8-octanedithiol;nitriles such as acetonitrile and acrylonitrile; fatty acids such asacetic acid and lactic acid; heterocyclic compounds such as furan,thiophene, pyrrole and pyridine; aromatic hydrocarbons such as benzene,toluene, xylene, ethylbenzene, cumene, n-butylbenzene, sec-butylbenzene,tert-butylbenzene, styrene, mesitylene, 1,2,4-trimethylbenzene,p-cymene, cyclohexylbenzene, diethylbenzene, pentylbenzene,dipentylbenzene, dodecylbenzene, ethynylbenzene, tetralin, anisole,phenetol, butyl phenyl ether, pentyl phenyl ether, veratrole,1,3-dimethoxybenzene, 1,2,4-trimethoxybenzene, 3,4,5-trimethoxytoluene,2-methoxytoluene, 2,5-dimethylanisole, o-chlorophenol, chlorobenzene,dichlorobenzene, trichlorobenzene, 1-chloronaphthalene,1-bromonaphthalene, 1-methylnaphthalene, o-diiodobenzene, acetophenone,2,3-benzofuran, 2,3-dihydrobenzofuran, 1,4-benzodioxane, phenyl acetate,methyl benzoate, cresol, aniline and nitrobenzene; and halogenhydrocarbons such as dichloromethane, 1,2-dichloroethylene,trichloroethylene, tetrachloroethylene, chloroform, carbontetrachloride, dichloroethane, trichloroethane, 1,3-dichloropropane,1,1,1,2-tetrachloroethane, 1,1,1,3-tetrachloropropane,1,2,2,3-tetrachloropropane, 1,1,2,3-tetrachloropropane,pentachloropropane, hexachloropropane, heptachloropropane,1-bromopropane, 1,2-dibromopropane, 2,2-dibromopropane,1,3-dibromopropane, 1,2,3-tribromopropane, 1,4-dibromobutane,1,5-dibromopentane, 1,6-dibromohexane, 1,7-dibromoheptane,1,8-dibromooctane, 1-iodopropane, 1,3-diiodopropane, 1,4-diiodobutane,1,5-diiodopentane, 1,6-diiodohexane, 1,7-diiodoheptane and1,8-diiodooctane. Examples of preferred solvents among these solventsinclude aromatic hydrocarbons such as toluene, xylene, mesitylene,1,2,4-trimethylbenzene, tetralin, anisole, phenetol, veratrole,1,3-dimethoxybenzene, 1,2,4-trimethoxybenzene, 3,4,5-trimethoxytoluene,2-methoxytoluene, 2,5-dimethylanisole, chlorobenzene, dichlorobenzene,trichlorobenzene and 1-chloronaphthalene; and halogen hydrocarbons suchas chloroform, dichloromethane, 1,2-dibromopropane, 1,3-dibromopropane,1,2,3-tribromopropane, 1,4-dibromobutane, 1,6-dibromohexane,1,8-dibromooctane, 1,3-diiodopropane, 1,4-diiodobutane,1,5-diiodopentane, 1,6-diiodohexane, 1,7-diiodoheptane and1,8-diiodooctane. In addition, two or more thereof may be mixed for use.

When an organic semiconductor layer is formed by mixing the electrondonating organic material using the conjugated polymer having astructure represented by formula (1) and the electron accepting organicmaterial, the electron donating organic material and the electronaccepting organic material are added to a solvent at the desired ratio,and by dissolving these by using a method such as heating, stirring, orirradiating with ultrasonic wave, and then the solution is applied ontothe transparent electrode. The photoelectric conversion efficiency ofthe photovoltaic device can be improved by using two or more kinds ofthe solvents as a mixture. This effect is presumably obtained since theelectron donating organic material and the electron accepting organicmaterial are phase-separated in a nano-level so that a carrier pathwhich forms a passing route of electrons and holes is formed.

The solvent to be combined therewith can be selected as an optimalcombination depending on the kinds of the electron donating organicmaterials and the electron accepting organic materials. When theelectron donating organic material using the conjugated polymer having astructure represented by formula (1) is used, examples of a preferredcombination of the above-mentioned solvents include a combination ofchloroform and chlorobenzene. In this case, the mixed volume ratiobetween chloroform and chlorobenzene is preferably 5:95 to 95:5, andmore preferably 10:90 to 90:10.

Moreover, when an organic semiconductor layer is formed by stacking theelectron accepting organic material on the electron donating organicmaterial using the conjugated polymer having a structure represented byformula (1), for example, after a solution of the electron donatingorganic material is applied to form a layer having the electron donatingorganic material, a solution of the electron accepting organic materialis applied thereon to form a layer. When each of the electron donatingorganic material and the electron accepting organic material is alow-molecular weight substance whose molecular weight is about 1000 orless, the layer may be formed by using a vapor deposition method.

The organic semiconductor layer may be formed by using any of thefollowing methods: a spin coating method, a blade coating method, a slitdie coating method, a screen printing method, a bar coating method, amold coating method, a print transfer method, a dip coating method, anink-jet method, a spraying method, a vacuum vapor deposition method, andthe like, and the formation method may be selected according to thecharacteristics of an organic semiconductor layer to be obtained such asfilm-thickness controlling and orientation controlling. For example,when the spin coating method is carried out, the electron donatingorganic material using the conjugated polymer having a structurerepresented by formula (1) and the electron accepting organic materialpreferably have a concentration of 1 to 20 g/l (weight of the electrondonating organic material and the electron accepting organic materialrelative to a volume of the solution containing the electron donatingorganic material, the electron accepting organic material and thesolvent), and by using this concentration, a homogeneous organicsemiconductor layer having a thickness of 5 to 200 nm can be easilyobtained.

To remove the solvent, the organic semiconductor layer thus formed maybe subjected to an annealing treatment under reduced pressure or in aninert atmosphere (in a nitrogen or argon atmosphere). The temperature ofthe annealing treatment is preferably 40° C. to 300° C., and morepreferably 50° C. to 200° C. By performing the annealing treatment, thestacked layers are mutually allowed to permeate each other through theinterface, and the effective contact areas consequently increase so thata short-circuit current can be increased. This annealing treatment maybe performed after the formation of the negative electrode.

Next, a metal electrode (corresponding to a negative electrode, in thiscase) made of Al or the like is formed on the organic semiconductorlayer by a vacuum vapor deposition method, a sputtering method or thelike. When an electron transporting layer is formed by the vacuum vapordeposition by using a low-molecular weight organic material, the metalelectrode is preferably formed, with the vacuum state being successivelymaintained.

When a hole transporting layer is disposed between the positiveelectrode and the organic semiconductor layer, a desired p-type organicsemiconductor material (PEDOT or the like) is applied onto the positiveelectrode by a spin coating method, a bar coating method, or a castingmethod by the use of a blade, and then the solvent is removed by using avacuum thermostat, a hot plate or the like to form the hole transportinglayer. When a low-molecular weight organic material, such asphthalocyanine derivatives and porphyrin derivatives, is used, a vacuumvapor deposition method by the use of a vacuum vapor deposition machinemay be employed.

When an electron transporting layer is disposed between the organicsemiconductor layer and the negative electrode, a desired n-type organicsemiconductor material (fullerene derivatives or the like) or n-typeinorganic semiconductor material (titanium oxide gel or the like) isapplied onto the organic semiconductor layer by a spin coating method, abar coating method, a casting method by the use of a blade, or aspraying method, and then the solvent is removed by using a vacuumthermostat, a hot plate or the like to form the electron transportinglayer. When a low-molecular weight organic material, such asphenanthroline derivatives and C₆₀, is used, a vacuum vapor depositionmethod by the use of a vacuum vapor deposition machine may be employed.

The photovoltaic device can be applicable to various photoelectricconversion devices in which its photoelectric conversion function,photo-rectifying function, or the like is utilized. For example, it isuseful for photoelectric cells (solar cells or the like), electrondevices (such as a photosensor, photoswitch, phototransistor or thelike), photorecording materials (photomemory or the like), imagingdevices, and the like.

EXAMPLES

Hereinafter, our polymers, materials and devices will be described inmore detail based on examples. In addition, this disclosure is notintended to be limited by the following examples. Also, among compoundswhich are used in the examples, those indicated by abbreviations areshown below.

-   ITO: Indium tin oxide-   PEDOT: Polyethylene dioxythiophene-   PSS: Polystyrene sulfonate-   PC₇₀BM: Phenyl C71 butyric acid methyl ester-   Eg: Band gap-   HOMO: Highest occupied molecular orbital-   Isc: Short-circuit current density-   Voc: Open Circuit Voltage-   FF: Fill factor-   η: Photoelectric conversion efficiency-   E-1 to E-6: Compound represented by the following formula

Additionally, for ¹H-NMR measurements, an FT-NMR device (JEOL JNM-EX270,manufactured by JEOL Ltd.) was used.

The average molecular weight (number-average molecular weight,weight-average molecular weight) was measured by GPC (high-speed GPCdevice HLC-8320GPC with transported chloroform, manufactured by TosohCorporation), and calculated by an absolute calibration curve method.The polymerization degree n was calculated based on the followingexpression:Polymerization degree n=[(Weight-average molecular weight)/(Molecularweight of repeating unit)

Moreover, with respect to an optical absorption edge wavelength,measurements were carried out on a thin film formed on glass with athickness of about 60 nm by using a U-3010-type spectrophotometermanufactured by Hitachi, Ltd., and based on the ultraviolet and visibleabsorption spectrum of the thin film (measured wavelength range: 300 to900 nm), the optical absorption edge wavelength was obtained.

The band gap (Eg) was calculated from the optical absorption edgewavelength based on the following expression. In addition, the thin filmwas formed by a spin coating method by using chloroform as a solvent.Eg (eV)=1240/Optical absorption edge wavelength of thin film (nm)

Further, the highest occupied molecular orbital (HOMO) level wasmeasured on a thin film formed on an ITO glass with a thickness of about60 nm by using a surface analyzing apparatus (Model AC-2 atmosphericultraviolet photoelectron spectrometer, manufactured by Rikenkiki Co.,Ltd.). In addition, the thin film was formed by a spin coating method byusing chloroform as a solvent.

In addition, it is possible to evaluate whether a material is anelectron donating organic material or an electron accepting organicmaterial, or p-type semiconductor characteristics or n-typesemiconductor characteristics by performing FET measurement or energylevel measurement of the thin film described above.

Synthesis Example 1

A compound A-1 was synthesized by the method shown in Scheme 1. Inaddition, a compound (1-i) and a compound (1-p) described in SynthesisExample 1 were synthesized by reference to a method described in“Journal of the American Chemical Society”, Vol. 131, pp. 7792-7799,2009, and a method described in “Angewandte Chem Internatioal Edition”,Vol. 50, pp. 9697-9702, 2011, respectively.

Methyl 2-thiophenecarboxylate (38 g (0.27 mol)) (produced by TokyoChemical Industry Co., Ltd.) and chloromethyl methyl ether (108 g (1.34mol)) (produced by Tokyo Chemical Industry Co., Ltd.) were stirred at 0°C., and to this was added tin tetrachloride (125 g (0.48 mol)) (producedby Wako Pure Chemical Industries, Ltd.) over 1 hour, and the resultingmixture was stirred at room temperature for 8 hours. After completion ofstirring, 100 ml of water was added gradually at 0° C., and theresulting mixture was extracted with chloroform three times. Theresulting organic layer was washed with a saturated saline, the solventwas dried with anhydrous magnesium sulfate, and then removed underreduced pressure. The resulting brown solid was recrystallized frommethanol to obtain a compound (1-b) as a light yellow solid (24.8 g,yield 39%). The result of ¹H-NMR measurement on compound (1-b) is shownbelow:

¹H-NMR (270 MHz, CDCl₃): 7.71 (s, 1H), 4.79 (s, 1H), 4.59 (s, 1H), 3.88(s, 3H) ppm.

The compound (1-b) (24.8 g (0.10 mmol)) was dissolved in methanol (1.2L) (produced by SASAKI CHEMICAL CO., LTD.) and stirred at 60° C., and tothis was added dropwise a methanol solution (100 ml) of sodium sulfide(8.9 g (0.11 mol)) (produced by Wako Pure Chemical Industries, Ltd.)over 1 hour, and the resulting mixture was stirred at 60° C. for 4hours. After completion of a reaction, the solvent was removed underreduced pressure, 200 ml of chloroform and 200 ml of water were added,and the resulting insoluble matter was separated by filtration. Theresulting organic layer was washed with water two times and with asaturated saline once, and dried with anhydrous magnesium sulfate, andthen the solvent was removed under reduced pressure. A product wasrefined by silica-gel column chromatography (eluent, chloroform) toobtain a compound (1-c) as a white solid (9.8 g, yield 48%). The resultof ¹H-NMR measurement on compound (1-c) is shown below:

¹H-NMR (270 MHz, CDCl₃): 7.48 (s, 1H), 4.19 (t, J=3.0 Hz, 2H), 4.05 (t,J=3.0 Hz, 2H), 3.87 (s, 3H) ppm.

To the compound (1-c) (9.8 g (49 mmol)) were added water (100 ml) andthen a 3 M aqueous sodium hydroxide solution (30 ml), and the resultingmixture was stirred at 80° C. for 4 hours. After completion of areaction, 15 ml of a concentrated hydrochloric acid was added at 0° C.,the resulting deposited solid matter was separated by filtration andwashed with water several times. The resulting solid matter was dried toobtain a compound (1-d) as a white solid (8.9 g, yield 98%). The resultof ¹H-NMR measurement on compound (1-d) is shown below:

¹H-NMR (270 MHz, DMSO-d₆): 7.46 (s, 1H), 4.18 (t, J=3.2 Hz, 2H), 4.01(t, J=3.2 Hz, 2H) ppm.

The compound (1-d) (1.46 g (7.8 mmol)) was dissolved in 60 ml of adehydrated tetrahydrofuran (produced by Wako Pure Chemical Industries,Ltd.) and stirred at −78° C., and to this was added dropwise an-butyllithium hexane solution (10.7 ml (17.2 mmol)) (1.6 M, produced byWako Pure Chemical Industries, Ltd.), and the resulting mixture wasstirred at −78° C. for 1 hour. Then, a dried tetrahydrofuran solution(20 ml) of N-fluorobenzene sulfonimide (3.19 g (10.1 mmol)) (produced byTokyo Chemical Industry Co., Ltd.) was added dropwise at −78° C. over 10minutes, and the resulting mixture was stirred at room temperature for12 hours. After completion of the reaction, 50 ml of water was addedgradually. A 3 M hydrochloric acid solution was added to allow a waterlayer to be acid, and then the resulting mixture was extracted withchloroform three times. After an organic layer was dried with anhydrousmagnesium sulfate, the solvent was distilled off under reduced pressure.After a by-product was removed by silica-gel column chromatography(eluent, ethyl acetate), the resulting product was re-crystallized fromethyl acetate to obtain a compound (1-e) as a light yellow powder (980mg, yield 61%). The result of ¹H-NMR measurement on compound (1-e) isshown below:

¹H-NMR (270 MHz, DMSO-d₆): 13.31 (brs, 1H), 4.20 (t, J=3.0 Hz, 2H), 4.03(t, J=3.0 Hz, 2H) ppm.

To 10 ml of a dehydrated dichloromethane (produced by Wako Pure ChemicalIndustries, Ltd.) solution of the compound (1-e) (800 mg (3.9 mmol))were added oxalyl chloride (1 ml) (Tokyo Chemical Industry Co., Ltd.)and then dimethylformamide (one drop) (produced by Wako Pure ChemicalIndustries, Ltd.), and the resulting mixture was stirred at roomtemperature for 3 hours. The solvent and excessive oxalyl chloride wereremoved under reduced pressure to obtain a compound (1-f) as a yellowoil. The compound (1-f) was used for a subsequent reaction as-is.

A dichloromethane solution (10 ml) of the compound (1-f, raw refinedproduct) was added to a dichloromethane solution (15 ml) of 1-octanol(1.3 g (10 mmol)) (produced by Wako Pure Chemical Industries, Ltd.) andtriethylamine (800 mg (8 mmol)) (produced by Wako Pure ChemicalIndustries, Ltd.) at room temperature, and the resulting mixture wasstirred at room temperature for 6 hours. The resulting reaction solutionwas washed with a 1 M hydrochloric acid solution two times, with wateronce and with a saturated saline once, and dried with anhydrousmagnesium sulfate, and then the solvent was distilled off under reducedpressure. The resulting product was refined by silica-gel columnchromatography (eluent, chloroform) to obtain a compound (1-g) as alight yellow solid (1.12 g, yield 90%). The result of ¹H-NMR measurementon compound (1-g) is shown below:

¹H-NMR (270 MHz, CDCl₃): 4.27 (t, J=6.7 Hz, 2H), 4.16 (t, J=3.0 Hz, 2H),4.01 (t, J=3.0 Hz, 2H), 1.72 (m, 2H), 1.5-1.3 (m, 12H), 0.88 (t, J=7.0Hz, 3H) ppm.

To 40 ml of an ethyl acetate solution of the compound (1-g) (1.1 g (3.5mmol)) was added an ethyl acetate solution (10 ml) of m-chlorobenzoicacid (630 mg (3.6 mmol)) (produced by Nacalai Tesque Inc.) at 0° C., andthe resulting mixture was stirred at room temperature for 5 hours. Afterthe solvent was removed under reduced pressure, 30 ml of acetic acidanhydride was added, and the resulting mixture was refluxed for 3 hours.After the solvent was removed again under reduced pressure, theresulting product was refined by silica-gel column chromatography(eluent, dichloromethane:hexane=1:1) to obtain a compound (1-h) as alight yellow oil (1.03 g, yield 94%). The result of ¹H-NMR measurementon compound (1-h) is shown below:

¹H-NMR (270 MHz, CDCl₃): 7.65 (d, J=2.7 Hz, 1H), 7.28 (dd, J=2.7 Hz and5.4 Hz, 1H), 4.31 (t, J=6.8 Hz, 2H), 1.75 (m, 2H), 1.42-1.29 (m, 12H),0.89 (t, J=6.8 Hz, 3H) ppm.

To 20 ml of a dimethylformamide solution of the compound (1-h) (1.0 g(3.2 mmol)) was added N-bromosuccinimide (1.25 g (7.0 mmol)) (producedby Wako Pure Chemical Industries, Ltd.) at room temperature, and theresulting mixture was stirred at room temperature for 3 hours. Aftercompletion of a reaction, 80 ml of ethyl acetate was added, and theresulting organic layer was washed with water five times and with asaturated saline once, and dried with anhydrous magnesium sulfate, andthen the solvent was distilled off under reduced pressure. The resultingproduct was refined by silica-gel column chromatography (eluent,chloroform:hexane=1:3) to obtain a compound (1-i) as a light yellowsolid (1.2 g, yield 79%). The result of ¹H-NMR measurement on compound(1-i) is shown below:

¹H-NMR (270 MHz, CDCl₃): 4.32 (t, J=6.5 Hz, 2H), 1.75 (m, 2H), 1.42-1.29(m, 12H), 0.89 (t, J=6.8 Hz, 3H) ppm.

To 300 ml of a dichloromethane solution of diethylamine (110 g (1.5mol)) (produced by Wako Pure Chemical Industries, Ltd.) was added3-thiophenecarbonyl chloride (100 g (0.68 mol)) (produced by Wako PureChemical Industries, Ltd.) at 0° C. over 1 hour, and the resultingmixture was stirred at room temperature for 3 hours. After completion ofstirring, 200 ml of water was added, and the resulting organic layer waswashed with water three times and with a saturated saline once. Afterthe organic layer was dried with anhydrous magnesium sulfate, thesolvent was distilled off under reduced pressure. A residue wasdistilled under reduced pressure to obtain a compound (1-k) as a lightorange-colored liquid (102 g, yield 82%). The result of ¹H-NMRmeasurement on compound (1-k) is shown below:

¹H-NMR (270 MHz, CDCl₃): 7.47 (dd, J=3.2 Hz and 1.0 Hz, 1H), 7.32 (dd,J=5.0 Hz and 3.2 Hz, 1H), 7.19 (dd, J=5.0 Hz and 1.0 Hz, 1H), 3.43 (brs,4H), 1.20 (t, J=6.5 Hz, 6H) ppm.

To 400 ml of a dehydrated tetrahydrofuran (produced by Wako PureChemical Industries, Ltd.) solution of the compound (1-k) (73.3 g (0.40mol)) was added dropwise a n-butyllithium hexane solution (250 ml (0.40mol)) (1.6 M, produced by Wako Pure Chemical Industries, Ltd.) at 0° C.over 30 minutes. After the dropwise addition, the resulting mixture wasstirred at room temperature for 4 hours. After completion of stirring,100 ml of water was added gradually, and the resulting reaction mixturewas stirred for a while and then poured in 800 ml of water. Theresulting deposited solid was separated by filtration and washed withwater, methanol and then hexane to obtain a compound (1-l) as a yellowsolid (23.8 g, yield 27%). The result of ¹H-NMR measurement on compound(1-l) is shown below:

¹H-NMR (270 MHz, CDCl₃): 7.69 (d, J=4.9 Hz, 2H), 7.64 (d, J=4.9 Hz, 2H)ppm.

To 400 ml of a dehydrated tetrahydrofuran (produced by Wako PureChemical Industries, Ltd.) solution of thiophene (42 g (0.50 mol)) wasadded dropwise a n-butyllithium hexane solution (250 ml (0.40 mol)) (1.6M, produced by Wako Pure Chemical Industries, Ltd.) at −78° C. over 30minutes. After the resulting reaction mixture was stirred at −78° C. for1 hour, 2-ethylhexylbromide (76.4 g (0.40 mol)) (produced by Wako PureChemical Industries, Ltd.) was added dropwise at −78° C. over 15minutes. After the resulting reaction solution was stirred at roomtemperature for 30 minutes, it was heated and stirred at 60° C. for 6hours. After completion of stirring, the reaction solution was cooled toroom temperature, and to this were added 200 ml of water and 200 ml ofether. The resulting organic layer was washed with water two times andwashed with a saturated saline, and dried with anhydrous magnesiumsulfate, and then the solvent was distilled off under reduced pressure.A residue was distilled under reduced pressure to obtain a compound(1-n) as a colorless liquid (28.3 g, 36%). The result of ¹H-NMRmeasurement on compound (1-n) is shown below:

¹H-NMR (270 MHz, CDCl₃): 7.11 (d, 4.9 Hz, 1H), 6.92 (dd, 4.9 Hz and 3.2Hz, 1H), 6.76 (d, J=3.2 Hz, 1H), 2.76 (d, J=6.8 Hz, 2H), 1.62 (m, 1H),1.4-1.3 (m, 8H), 0.88 (m, 6H) ppm.

To 400 ml of a dehydrated tetrahydrofuran (produced by Wako PureChemical Industries, Ltd.) solution of the compound (1-n) (17.5 g (89mmol)) was added dropwise a n-butyllithium hexane solution (57 ml (89mmol)) (1.6 M, produced by Wako Pure Chemical Industries, Ltd.) at 0° C.over 30 minutes. After the resulting reaction solution was stirred at50° C. for 1 hour, the compound (1-l) (4.9 g (22 mmol)) was added at 50°C. and the resulting mixture was stirred for 1 hour as-is. Aftercompletion of stirring, the reaction solution was cooled to 0° C., andto this was added a solution formed by dissolving tin chloride dihydrate(39.2 g (175 mmol)) (produced by Wako Pure Chemical Industries, Ltd.) ina 10% hydrochloric acid solution (80 mL), and the resulting mixture wasstirred at room temperature for 1 hour. After completion of stirring,200 ml of water and 200 ml of diethyl ether were added, and theresulting organic layer was washed with water two times and washed witha saturated saline. After the organic layer was dried with anhydrousmagnesium sulfate, the solvent was distilled off under reduced pressure.The resulting product was refined by silica-gel column chromatography(eluent, hexane) to obtain a compound (1-o) as a yellow oil (7.7 g,yield 59%). The result of ¹H-NMR measurement on compound (1-o) is shownbelow:

¹H-NMR (270 MHz, CDCl₃): 7.63 (d, J=5.7 Hz, 1H), 7.45 (d, J=5.7 Hz, 1H),7.29 (d, J=3.6 Hz, 1H), 6.88 (d, J=3.6 Hz, 1H), 2.86 (d, J=7.0 Hz, 2H),1.70-1.61 (m, 1H), 1.56-1.41 (m, 8H), 0.97-0.89 (m, 6H) ppm.

To 25 ml of a dehydrated tetrahydrofuran (produced by Wako Pure ChemicalIndustries, Ltd.) solution of the compound (1-o) (870 mg (1.5 mmol)) wasadded a n-butyllithium hexane solution (2.0 ml (3.3 mmol)) (1.6 M,produced by Wako Pure Chemical Industries, Ltd.) at −78° C. by using asyringe, and the resulting mixture was stirred at −78° C. for 30 minutesand at room temperature for 30 minutes. After the resulting reactionmixture was cooled to −78° C., trimethyltin chloride (800 mg (4.0 mmol))(produced by Wako Pure Chemical Industries, Ltd.) was added at −78° C.at a time, and the resulting mixture was stirred at room temperature for4 hours. After completion of stirring, 50 ml of diethyl ether and 50 mlof water were added, and after the resulting mixture was stirred at roomtemperature for 5 minutes, the resulting organic layer was washed withwater two times and washed with a saturated saline. After the solventwas dried with anhydrous sodium sulfate, the solvent was distilled offunder reduced pressure. The resulting orange-colored oil wasrecrystallized from ethanol to obtain a compound (1-p) as a light yellowsolid (710 mg, yield 52%). The result of ¹H-NMR measurement on compound(1-p) is shown below:

¹H-NMR (270 MHz, CDCl₃): 7.68 (s, 2H), 7.31 (d, J=3.2 Hz, 2H), 6.90 (d,J=3.2 Hz, 2H), 2.87 (d, J=6.2 Hz, 4H), 1.69 (m, 2H), 1.40-1.30 (m, 16H),1.0-0.9 (m, 12H), 0.39 (s, 18H) ppm.

The compound (1-i) (71 mg (0.15 mmol)) and the compound (1-p) (136 mg(0.15 mmol)) were dissolved in toluene (4 ml) (produced by Wako PureChemical Industries, Ltd.) and dimethylformamide (1 ml) (produced byWako Pure Chemical Industries, Ltd.), and to this was addedtetrakis(triphenyl phosphine)palladium (5 mg) (produced by TokyoChemical Industry Co., Ltd.), and the resulting mixture was stirred at100° C. for 15 hours in a nitrogen atmosphere. Next, to this was added15 mg of bromobenzene (produced by Tokyo Chemical Industry Co., Ltd.),and stirred at 100° C. for 1 hour. Then, 40 mg of tributyl(2-thienyl)tin(produced by Tokyo Chemical Industry Co., Ltd.) was added and theresulting mixture was further stirred at 100° C. for 1 hour. Aftercompletion of stirring, the resulting reaction mixture was cooled toroom temperature and poured in 100 ml of methanol. The resultingdeposited solid matter was separated by filtration and washed withmethanol, water and then acetone. Then, the solid matter was washed withacetone and hexane in this order using a Soxhlet extractor. Next, afterthe solid matter was dissolved in chloroform, and resulting chloroformsolution was passed through celite (produced by Nacalai Tesque Inc.) andsubsequently through a silica-gel column (eluent: chloroform), thesolvent was distilled off under reduced pressure. The resulting solidmatter was dissolved in chloroform again, and then re-precipitated inmethanol to obtain a compound A-1 (85 mg). The compound A-1 had a weightaverage molecular weight of 25000 and a number average molecular weightof 16000. Further, the compound A-1 had an optical absorption edgewavelength of 783 nm, a bandgap (Eg) of 1.58 eV, and the highestoccupied molecular orbital (HOMO) level of −4.95 eV.

Synthesis Example 2

A compound A-2 was synthesized by the method shown in Scheme 2.

To 30 ml of a dehydrated dichloromethane (produced by Wako Pure ChemicalIndustries, Ltd.) solution of the compound (1-e) (2.4 g (11.7 mmol))were added oxalyl chloride (3 ml) (Tokyo Chemical Industry Co., Ltd.)and then dimethylformamide (one drop) (produced by Wako Pure ChemicalIndustries, Ltd.), and the resulting mixture was stirred at roomtemperature for 3 hours. The solvent and excessive oxalyl chloride wereremoved under reduced pressure to obtain a compound (2-a) as a yellowoil. The compound (2-a) was used for a subsequent reaction as-is.

A dichloromethane solution (20 ml) of the compound (2-a, raw refinedproduct) was added to a dichloromethane solution (40 ml) ofN-methoxy-N-methylamine hydrochloride (2.7 g (21 mmol)) (produced byWako Pure Chemical Industries, Ltd.) and triethylamine (5.1 g (50 mmol))(produced by Wako Pure Chemical Industries, Ltd.) at room temperature,and the resulting mixture was stirred at room temperature for 6 hours.The resulting reaction solution was washed with a 1 M hydrochloric acidsolution two times, with water once and with a saturated saline once,and dried with anhydrous magnesium sulfate, and then the solvent wasdistilled off under reduced pressure. The resulting product was refinedby silica-gel column chromatography (eluent, chloroform) to obtain acompound (2-b) as a light yellow solid (1.8 g, yield 62%). The result of¹H-NMR measurement on compound (2-b) is shown below:

¹H-NMR (270 MHz, CDCl₃): 4.17 (s, 2H), 4.04 (s, 2H), 3.73 (s, 1H), 3.36(s, 1H) ppm.

To 60 ml of a tetrahydrofuran solution of the compound (2-b) (1.5 g (6.1mmol)) was added dropwise a nonyl-butyllithium diethyl ether solution(10 ml (10 mmol)) (1 M, produced by Chemical Soft R&D Inc.) at 0° C.over 10 minutes, and the resulting mixture was stirred at 0° C. for 1hour. After completion of stirring, 80 ml of diethyl ether was added,and the resulting mixture was washed with water two times and with asaturated saline once, and dried with anhydrous magnesium sulfate, andthen the solvent was distilled off under reduced pressure. The resultingproduct was refined by silica-gel column chromatography (eluent,chloroform:hexane=1:2) to obtain a compound (2-c) as a light yellowsolid (1.0 g, yield 54%). The result of ¹H-NMR measurement on compound(2-c) is shown below:

¹H-NMR (270 MHz, CDCl₃): 4.16 (s, 2H), 4.01 (s, 2H), 2.82 (t, J=5.9 Hz,2H), 1.70 (m, 2H), 1.4-1.2 (m, 14H), 0.88 (t, J=6.7 Hz, 3H) ppm.

To 40 ml of an ethyl acetate solution of the compound (2-c) (1.0 g (3.2mmol)) was added an ethyl acetate solution (10 ml) of m-chlorobenzoicacid (600 mg (3.4 mmol)) (produced by Nacalai Tesque Inc.) at 0° C., andthe resulting mixture was stirred at room temperature for 5 hours. Afterthe solvent was removed under reduced pressure, 30 ml of acetic acidanhydride was added, and the resulting mixture was refluxed for 3 hours.After the solvent was removed again under reduced pressure, theresulting product was refined by silica-gel column chromatography(eluent, chloroform:hexane=1:1) to obtain a compound (2-d) as a lightyellow oil (780 mg, yield 78%). The result of ¹H-NMR measurement oncompound (2-d) is shown below:

¹H-NMR (270 MHz, CDCl₃): 7.70 (s, 1H), 7.27 (s, 1H), 2.95 (t, J=6.2 Hz,2H), 1.72 (m, 2H), 1.4-1.2 (m, 14H), 0.86 (t, J=6.8 Hz, 3H) ppm.

To 20 ml of a dimethylformamide solution of the compound (2-d) (750 mg(2.4 mmol)) was added N-bromosuccinimide (940 mg (5.3 mmol)) (producedby Wako Pure Chemical Industries, Ltd.) at room temperature, and theresulting mixture was stirred at room temperature for 3 hours. Aftercompletion of a reaction, 80 ml of ethyl acetate was added, and theresulting organic layer was washed with water five times and with asaturated saline once, and dried with anhydrous magnesium sulfate, andthen the solvent was distilled off under reduced pressure. The resultingproduct was refined by silica-gel column chromatography (eluent,chloroform:hexane=1:3) to obtain a compound (2-e) as a light yellowsolid (810 mg, yield 72%). The result of ¹H-NMR measurement on compound(2-e) is shown below:

¹H-NMR (270 MHz, CDCl₃): 2.93 (t, J=7.3 Hz, 2H), 1.72 (m, 2H), 1.4-1.2(m, 14H), 0.88 (t, J=7.0 Hz, 3H) ppm.

The compound (2-e) (71 mg (0.15 mmol)) and the compound (1-p) (136 mg(0.15 mmol)) were dissolved in toluene (4 ml) (produced by Wako PureChemical Industries, Ltd.) and dimethylformamide (1 ml) (produced byWako Pure Chemical Industries, Ltd.), and to this was addedtetrakis(triphenyl phosphine)palladium (5 mg) (produced by TokyoChemical Industry Co., Ltd.), and the resulting mixture was stirred at100° C. for 15 hours in a nitrogen atmosphere. Next, to this was added15 mg of bromobenzene (produced by Tokyo Chemical Industry Co., Ltd.),and stirred at 100° C. for 1 hour. Then, 40 mg of tributyl(2-thienyl)tin(produced by Tokyo Chemical Industry Co., Ltd.) was added and theresulting mixture was further stirred at 100° C. for 1 hour. Aftercompletion of stirring, the resulting reaction mixture was cooled toroom temperature and poured in 100 ml of methanol. The resultingdeposited solid matter was separated by filtration and washed withmethanol, water and then acetone. Then, the solid matter was washed withacetone and hexane in this order using a Soxhlet extractor. Next, afterthe solid matter was dissolved in chloroform, and resulting chloroformsolution was passed through celite (produced by Nacalai Tesque Inc.) andsubsequently through a silica-gel column (eluent: chloroform), thesolvent was distilled off under reduced pressure. The resulting solidmatter was dissolved in chloroform again, and then re-precipitated inmethanol to obtain a compound A-2 (105 mg). The compound A-2 had aweight average molecular weight of 18000 and a number average molecularweight of 13000. Further, the compound A-2 had an optical absorptionedge wavelength of 790 nm, a bandgap (Eg) of 1.57 eV, and the highestoccupied molecular orbital (HOMO) level of −5.01 eV.

Synthesis Example 3

A compound A-3 was synthesized by the method shown in Scheme 3.

To 80 ml of a dehydrated dichloromethane (produced by Wako Pure ChemicalIndustries, Ltd.) solution of the compound (1-d) (5.0 g (26.8 mmol))were added oxalyl chloride (8 ml) (Tokyo Chemical Industry Co., Ltd.)and then dimethylformamide (two drops) (produced by Wako Pure ChemicalIndustries, Ltd.), and the resulting mixture was stirred at roomtemperature for 3 hours. The solvent and excessive oxalyl chloride wereremoved under reduced pressure to obtain a compound (3-a) as a yellowoil. The compound (3-a) was used for a subsequent reaction as-is.

A dichloromethane solution (40 ml) of the compound (3-a, raw refinedproduct) was added to a dichloromethane solution (100 ml) ofN-methoxy-N-methylamine hydrochloride (4.7 g (48 mmol)) (produced byWako Pure Chemical Industries, Ltd.) and triethylamine (11.5 g (115mmol)) (produced by Wako Pure Chemical Industries, Ltd.) at roomtemperature, and the resulting mixture was stirred at room temperaturefor 6 hours. The resulting reaction solution was washed with a 1 Mhydrochloric acid solution two times, with water once and with asaturated saline once, and dried with anhydrous magnesium sulfate, andthen the solvent was distilled off under reduced pressure. The resultingproduct was refined by silica-gel column chromatography (eluent,chloroform) to obtain a compound (3-b) as a light yellow solid (5.6 g,yield 91%). The result of ¹H-NMR measurement on compound (3-b) is shownbelow:

¹H-NMR (270 MHz, CDCl₃): 7.64 (s, 1H), 4.20 (s, 2H), 4.07 (s, 2H), 3.77(s, 1H), 3.36 (s, 1H) ppm

To 60 ml of a tetrahydrofuran solution of the compound (3-b) (1.5 g (6.5mmol)) was added dropwise a nonylmagnesium bromide diethyl ethersolution (10 ml (10 mmol)) (1 M, produced by Aldrich Corporation) at 0°C. over 10 minutes, and the resulting mixture was stirred at 0° C. for 1hour. After completion of stirring, 80 ml of diethyl ether was added,and the resulting mixture was washed with water two times and with asaturated saline once, and dried with anhydrous magnesium sulfate, andthen the solvent was distilled off under reduced pressure. The resultingproduct was refined by silica-gel column chromatography (eluent,chloroform:hexane=1:2) to obtain a compound (3-c) as a light yellowsolid matter (1.7 g, yield 87%). The result of ¹H-NMR measurement oncompound (3-c) is shown below:

¹H-NMR (270 MHz, CDCl₃): 7.38 (s, 1H), 4.20 (s, 2H), 4.06 (s, 2H), 2.81(t, J=7.3 Hz, 2H), 1.70 (m, 2H), 1.4-1.2 (m, 14H), 0.88 (t, J=7.0 Hz,3H) ppm.

To 60 ml of an ethyl acetate solution of the compound (3-c) (1.5 g (5.1mmol)) was added an ethyl acetate solution (10 ml) of m-chlorobenzoicacid (900 mg (5.2 mmol)) (produced by Nacalai Tesque Inc.) at 0° C., andthe resulting mixture was stirred at room temperature for 5 hours. Afterthe solvent was removed under reduced pressure, 40 ml of acetic acidanhydride was added, and the resulting mixture was refluxed for 3 hours.After the solvent was removed again under reduced pressure, theresulting product was refined by silica-gel column chromatography(eluent, chloroform:hexane=1:1) to obtain a compound (3-d) as a lightyellow oil (1.2 g, yield 81%). The result of ¹H-NMR measurement oncompound (3-d) is shown below:

¹H-NMR (270 MHz, CDCl₃): 7.64 (s, 1H), 7.60 (s, 1H), 7.28 (s, 1H), 2.90(t, J=7.3 Hz, 2H), 1.76 (m, 2H), 1.4-1.2 (m, 14H), 0.88 (t, J=6.7 Hz,3H) ppm.

To 30 ml of a dimethylformamide solution of the compound (3-d) (1.0 g(3.4 mmol)) was added N-bromosuccinimide (1.33 g (7.5 mmol)) (producedby Wako Pure Chemical Industries, Ltd.) at room temperature, and theresulting mixture was stirred at room temperature for 3 hours. Aftercompletion of a reaction, 80 ml of ethyl acetate was added, and theresulting organic layer was washed with water five times and with asaturated saline once, and dried with anhydrous magnesium sulfate, andthen the solvent was distilled off under reduced pressure. The resultingproduct was refined by silica-gel column chromatography (eluent,chloroform:hexane=1:3) to obtain a compound (3-e) as a light yellowsolid (1.2 g, yield 78%). The result of ¹H-NMR measurement on compound(3-e) is shown below:

¹H-NMR (270 MHz, CDCl₃): 7.39 (s, 1H), 2.90 (t, J=7.3 Hz, 2H), 1.75 (m,2H), 1.4-1.2 (m, 14H), 0.88 (t, J=7.0 Hz, 3H) ppm.

The compound (3-e) (68 mg (0.15 mmol)) and the compound (1-p) (136 mg(0.15 mmol)) were dissolved in toluene (4 ml) (produced by Wako PureChemical Industries, Ltd.) and dimethylformamide (1 ml) (produced byWako Pure Chemical Industries, Ltd.), and to this was addedtetrakis(triphenyl phosphine)palladium (5 mg) (produced by TokyoChemical Industry Co., Ltd.), and the resulting mixture was stirred at100° C. for 15 hours in a nitrogen atmosphere. Next, to this was added15 mg of bromobenzene (produced by Tokyo Chemical Industry Co., Ltd.),and stirred at 100° C. for 1 hour. Then, 40 mg of tributyl(2-thienyl)tin(produced by Tokyo Chemical Industry Co., Ltd.) was added and theresulting mixture was further stirred at 100° C. for 1 hour. Aftercompletion of stirring, the resulting reaction mixture was cooled toroom temperature and poured in 100 ml of methanol. The resultingdeposited solid matter was separated by filtration and washed withmethanol, water and then acetone. Then, the solid matter was washed withacetone and hexane in this order using a Soxhlet extractor. Next, afterthe solid matter was dissolved in chloroform, and resulting chloroformsolution was passed through celite (produced by Nacalai Tesque Inc.) andsubsequently through a silica-gel column (eluent: chloroform), thesolvent was distilled off under reduced pressure. The resulting solidmatter was dissolved in chloroform again, and then re-precipitated inmethanol to obtain a compound A-3 (102 mg). The compound A-3 had aweight average molecular weight of 36000 and a number average molecularweight of 19000. Further, the compound A-3 had an optical absorptionedge wavelength of 800 nm, a bandgap (Eg) of 1.55 eV, and the highestoccupied molecular orbital (HOMO) level of −5.00 eV.

Synthesis Example 4

A compound A-4 was synthesized by the method shown in Scheme 4. Inaddition, a compound (4-a) described in Synthesis Example 4 wassynthesized by reference to a method described in “Journal of theAmerican Chemical Society”, Vol. 131, pp. 7792-7799, 2009.

The compound (1-i) (56.7 mg (0.12 mmol)), the compound (4-a) (13.6 mg(0.03 mmol)) and the compound (1-p) (136 mg (0.15 mmol)) were dissolvedin toluene (4 ml) (produced by Wako Pure Chemical Industries, Ltd.) anddimethylformamide (1 ml) (produced by Wako Pure Chemical Industries,Ltd.), and to this was added tetrakis(triphenyl phosphine)palladium (5mg) (produced by Tokyo Chemical Industry Co., Ltd.), and the resultingmixture was stirred at 100° C. for 15 hours in a nitrogen atmosphere.Next, to this was added 15 mg of bromobenzene (produced by TokyoChemical Industry Co., Ltd.), and stirred at 100° C. for 1 hour. Then,40 mg of tributyl(2-thienyl)tin (produced by Tokyo Chemical IndustryCo., Ltd.) was added and the resulting mixture was further stirred at100° C. for 1 hour. After completion of stirring, the resulting reactionmixture was cooled to room temperature and poured in 100 ml of methanol.The resulting deposited solid matter was separated by filtration andwashed with methanol, water and then acetone. Then, the solid matter waswashed with acetone and hexane in this order using a Soxhlet extractor.Next, after the solid matter was dissolved in chloroform, and resultingchloroform solution was passed through celite (produced by NacalaiTesque Inc.) and subsequently through a silica-gel column (eluent:chloroform), the solvent was distilled off under reduced pressure. Theresulting solid matter was dissolved in chloroform again, and thenre-precipitated in methanol to obtain a compound A-4 (92 mg). Thecompound A-4 had a weight average molecular weight of 28000 and a numberaverage molecular weight of 17000. Further, the compound A-4 had anoptical absorption edge wavelength of 784 nm, a bandgap (Eg) of 1.58 eV,and the highest occupied molecular orbital (HOMO) level of −4.95 eV.

Synthesis Example 5

A compound B-1 was synthesized by the method shown in Scheme 5. Inaddition, a compound (5-c) and (5-e) described in Synthesis Example 5were synthesized by reference to a method described in “Journal of theAmerican Chemical Society”, Vol. 131, pp. 7792-7799, 2009.

To 15 ml of a dehydrated dichloromethane (produced by Wako Pure ChemicalIndustries, Ltd.) solution of the compound (1-e) (1.5 g (7.8 mmol)) wereadded oxalyl chloride (2 ml) (Tokyo Chemical Industry Co., Ltd.) andthen dimethylformamide (one drop) (produced by Wako Pure ChemicalIndustries, Ltd.), and the resulting mixture was stirred at roomtemperature for 3 hours. The solvent and excessive oxalyl chloride wasremoved under reduced pressure to obtain a compound (1-f) as a yellowoil. The compound (1-f) was used for a subsequent reaction as-is.

A dichloromethane solution (10 ml) of the compound (1-f, raw refinedproduct) was added to a dichloromethane solution (15 ml) of2-ethylhexanol (2.6 g (20 mmol)) (produced by Wako Pure ChemicalIndustries, Ltd.) and triethylamine (1 g (10 mmol)) (produced by WakoPure Chemical Industries, Ltd.) at room temperature, and the resultingmixture was stirred at room temperature for 6 hours. The resultingreaction solution was washed with a 1 M hydrochloric acid solution twotimes, with water once and with a saturated saline once, and dried withanhydrous magnesium sulfate, and then the solvent was distilled offunder reduced pressure. The resulting product was passed through asilica-gel column (eluent: chloroform), and the solvent was distilledoff under reduced pressure to obtain a compound (5-a) as a light yellowoil (raw refined product). The compound (5-a) was used for a subsequentreaction as-is.

To 60 ml of an ethyl acetate solution of the compound (5-a, raw refinedproduct) was added dropwise an ethyl acetate solution (20 ml) ofm-chlorobenzoic acid (1.37 g (7.8 mmol)) (produced by Nacalai TesqueInc.) at 0° C., and the resulting mixture was stirred at roomtemperature for 5 hours. After the solvent was removed under reducedpressure, 30 ml of acetic acid anhydride was added, and the resultingmixture was heated/refluxed for 3 hours. After the solvent was removedagain under reduced pressure, the resulting product was refined bysilica-gel column chromatography (eluent, dichloromethane:hexane=1:1) toobtain a compound (5-b) as a light yellow oil (1.30 g). The result of¹H-NMR measurement on compound (5-b) is shown below:

¹H-NMR (270 MHz, CDCl₃): 7.66 (s, 1H), 7.28 (s, 1H), 4.23 (d, J=5.9 Hz,2H), 1.61 (m, 1H), 1.5-1.2 (m, 8H), 0.9 (m, 6H) ppm.

To 20 ml of a dimethylformamide solution of the compound (5-b) (1.0 g(3.2 mmol)) was added N-bromosuccinimide (1.25 g (7.0 mmol)) (producedby Wako Pure Chemical Industries, Ltd.) at room temperature, and theresulting mixture was stirred at room temperature for 3 hours. Aftercompletion of a reaction, 80 ml of ethyl acetate was added, and theresulting organic layer was washed with water five times and with asaturated saline once, and dried with anhydrous magnesium sulfate, andthen the solvent was distilled off under reduced pressure. The resultingproduct was refined by silica-gel column chromatography (eluent,chloroform:hexane=1:3) to obtain a compound (5-c) as a light yellow oil(1.1 g, yield 73%). The result of ¹H-NMR measurement on compound (5-c)is shown below:

¹H-NMR (270 MHz, CDCl₃): 4.25 (d, J=5.7 Hz, 2H), 1.69 (s, 1H), 1.5-1.2(m, 6H), 0.94 (t, J=6.8 Hz, 3H), 0.91 (t, J=6.8 Hz, 3H) ppm.

To the compound (1-l) (8.4 g (38 mmol)) were added ethanol (30 ml), a20% aqueous sodium hydroxide solution (120 ml), and a zinc powder (5.3 g(80 mmol)) (produced by Wako Pure Chemical Industries, Ltd.), and theresulting reaction mixture was refluxed for 1 hour. To the resultingproduct was added 2-ethylhexylbromide (25.0 g (0.11 mol)) (produced byWako Pure Chemical Industries, Ltd.), and the resulting reaction mixturewas further refluxed for 4 hours. After completion of a reaction, thereaction mixture was cooled to room temperature, and to this were added100 ml of water and 100 ml of chloroform. After the reaction mixture waspassed through celite to be filtered, a water layer was extracted withchloroform two times. The resulting organic layer was washed with watertwo times and with a saturated saline once, and dried with anhydrousmagnesium sulfate, and then the solvent was distilled off under reducedpressure. The resulting product was refined by silica-gel columnchromatography (eluent, chloroform:hexane=1:5) to obtain a compound(5-d) as a light yellow oil (4.4 g, yield 26%). The result of ¹H-NMRmeasurement on compound (5-d) is shown below:

¹H-NMR (270 MHz, CDCl₃): 7.47 (d, J=5.7 Hz, 2H), 7.36 (d, J=5.7 Hz, 2H),4.18 (d, J=5.1 Hz, 4H), 1.9-0.8 (m, 34H) ppm.

To 50 ml of a dehydrated tetrahydrofuran (produced by Wako Pure ChemicalIndustries, Ltd.) solution of the compound (5-d) (1.47 g (3.3 mmol)) wasadded dropwise a n-butyllithium hexane solution (13.2 ml (8.3 mmol))(1.6 M, produced by Wako Pure Chemical Industries, Ltd.) at −78° C.After the reaction solution was stirred at −78° C. for 30 minutes and atroom temperature for 30 minutes, and to this was added trimethyltinchloride (2.0 g (10 mol)) (produced by Tokyo Chemical Industry Co.,Ltd.) at −78° C. After the reaction solution was stirred at roomtemperature for 6 hours, 80 ml of hexane and 20 ml of water were added,and the resulting organic layer was washed with water three times. Afterthe organic layer was dried with anhydrous sodium sulfate, the solventwas distilled off under reduced pressure. The resulting product wasrecrystallized from isopropanol to obtain a compound (5-e) as a whitesolid (1.60 g, yield 63%). The result of ¹H-NMR measurement on compound(5-e) is shown below:

¹H-NMR (270 MHz, CDCl₃): 7.51 (s, 2H), 4.19 (d, J=5.1 Hz, 4H), 1.8-1.4(m, 22H), 1.03 (t, J=7.3 Hz, 6H), 0.94 (t, J=7.3 Hz, 6H), 0.44 (s, 18H)ppm.

The compound (5-c) (71 mg (0.15 mmol)) and the compound (5-e) (116 mg(0.15 mmol)) were dissolved in toluene (4 ml) (produced by Wako PureChemical Industries, Ltd.) and dimethylformamide (1 ml) (produced byWako Pure Chemical Industries, Ltd.), and to this was addedtetrakis(triphenyl phosphine)palladium (5 mg) (produced by TokyoChemical Industry Co., Ltd.), and the resulting mixture was stirred at100° C. for 15 hours in a nitrogen atmosphere. Next, to this was added15 mg of bromobenzene (produced by Tokyo Chemical Industry Co., Ltd.),and stirred at 100° C. for 1 hour. Then, 40 mg of tributyl(2-thienyl)tin(produced by Tokyo Chemical Industry Co., Ltd.) was added and theresulting mixture was further stirred at 100° C. for 1 hour. Aftercompletion of stirring, the resulting reaction mixture was cooled toroom temperature and poured in 100 ml of methanol. The resultingdeposited solid matter was separated by filtration and washed withmethanol, water and then acetone. Then, the solid matter was washed withacetone and hexane in this order using a Soxhlet extractor. Next, afterthe solid matter was dissolved in chloroform, and resulting chloroformsolution was passed through celite (produced by Nacalai Tesque Inc.) andsubsequently through a silica-gel column (eluent: chloroform), thesolvent was distilled off under reduced pressure. The resulting solidmatter was dissolved in chloroform again, and then re-precipitated inmethanol to obtain a compound B-1 (73 mg). The compound B-1 had a weightaverage molecular weight of 31000 and a number average molecular weightof 13000. Further, the compound B-1 had an optical absorption edgewavelength of 754 nm, a bandgap (Eg) of 1.64 eV, and the highestoccupied molecular orbital (HOMO) level of −5.09 eV.

Synthesis Example 6

A compound B-2 was synthesized by the method shown in Scheme 6.

The compound (1-i) (71 mg (0.15 mmol)) and the compound (5-e) (116 mg(0.15 mmol)) were dissolved in toluene (4 ml) (produced by Wako PureChemical Industries, Ltd.) and dimethylformamide (1 ml) (produced byWako Pure Chemical Industries, Ltd.), and to this was addedtetrakis(triphenyl phosphine)palladium (5 mg) (produced by TokyoChemical Industry Co., Ltd.), and the resulting mixture was stirred at100° C. for 15 hours in a nitrogen atmosphere. Next, to this was added15 mg of bromobenzene (produced by Tokyo Chemical Industry Co., Ltd.),and stirred at 100° C. for 1 hour. Then, 40 mg of tributyl(2-thienyl)tin(produced by Tokyo Chemical Industry Co., Ltd.) was added and theresulting mixture was further stirred at 100° C. for 1 hour. Aftercompletion of stirring, the resulting reaction mixture was cooled toroom temperature and poured in 100 ml of methanol. The resultingdeposited solid matter was separated by filtration and washed withmethanol, water and then acetone. Then, the solid matter was washed withacetone and hexane in this order using a Soxhlet extractor. Next, afterthe solid matter was dissolved in chloroform, and resulting chloroformsolution was passed through celite (produced by Nacalai Tesque Inc.) andsubsequently through a silica-gel column (eluent: chloroform), thesolvent was distilled off under reduced pressure. The resulting solidmatter was dissolved in chloroform again, and then re-precipitated inmethanol to obtain a compound B-2 (82 mg). The compound B-2 had a weightaverage molecular weight of 22000 and a number average molecular weightof 11000. Further, the compound B-2 had an optical absorption edgewavelength of 755 nm, a bandgap (Eg) of 1.64 eV, and the highestoccupied molecular orbital (HOMO) level of −5.06 eV.

Synthesis Example 7

A compound B-3 was synthesized by the method shown in Scheme 7. Inaddition, a compound (7-a) described in Synthesis Example 7 wassynthesized by reference to a method described in “Journal of theAmerican Chemical Society”, Vol. 131, pp. 7792-7799, 2009.

The compound (7-a) (68 mg (0.15 mmol)) and the compound (1-p) (136 mg(0.15 mmol)) were dissolved in toluene (4 ml) (produced by Wako PureChemical Industries, Ltd.) and dimethylformamide (1 ml) (produced byWako Pure Chemical Industries, Ltd.), and to this was addedtetrakis(triphenyl phosphine)palladium (5 mg) (produced by TokyoChemical Industry Co., Ltd.), and the resulting mixture was stirred at100° C. for 15 hours in a nitrogen atmosphere. Next, to this was added15 mg of bromobenzene (produced by Tokyo Chemical Industry Co., Ltd.),and stirred at 100° C. for 1 hour. Then, 40 mg of tributyl(2-thienyl)tin(produced by Tokyo Chemical Industry Co., Ltd.) was added and theresulting mixture was further stirred at 100° C. for 1 hour. Aftercompletion of stirring, the resulting reaction mixture was cooled toroom temperature and poured in 100 ml of methanol. The resultingdeposited solid matter was separated by filtration and washed withmethanol, water and then acetone. Then, the solid matter was washed withacetone and hexane in this order using a Soxhlet extractor. Next, afterthe solid matter was dissolved in chloroform, and resulting chloroformsolution was passed through celite (produced by Nacalai Tesque Inc.) andsubsequently through a silica-gel column (eluent: chloroform), thesolvent was distilled off under reduced pressure. The resulting solidmatter was dissolved in chloroform again, and then re-precipitated inmethanol to obtain a compound B-3 (80 mg). The compound B-3 had a weightaverage molecular weight of 35000 and a number average molecular weightof 17000. Further, the compound B-3 had an optical absorption edgewavelength of 784 nm, a bandgap (Eg) of 1.58 eV, and the highestoccupied molecular orbital (HOMO) level of −4.91 eV.

Synthesis Example 8

A compound B-4 was synthesized by the method shown in Scheme 8. Inaddition, a compound (8-a) described in Synthesis Example 8 wassynthesized by reference to a method described in “Journal of theAmerican Chemical Society”, Vol. 131, pp. 15586-15587, 2009.

The compound (5-a) (64 mg (0.15 mmol)) and the compound (1-p) (136 mg(0.15 mmol)) were dissolved in toluene (4 ml) (produced by Wako PureChemical Industries, Ltd.) and dimethylformamide (1 ml) (produced byWako Pure Chemical Industries, Ltd.), and to this was addedtetrakis(triphenyl phosphine)palladium (5 mg) (produced by TokyoChemical Industry Co., Ltd.), and the resulting mixture was stirred at100° C. for 15 hours in a nitrogen atmosphere. Next, to this was added15 mg of bromobenzene (produced by Tokyo Chemical Industry Co., Ltd.),and stirred at 100° C. for 1 hour. Then, 40 mg of tributyl(2-thienyl)tin(produced by Tokyo Chemical Industry Co., Ltd.) was added and theresulting mixture was further stirred at 100° C. for 1 hour. Aftercompletion of stirring, the resulting reaction mixture was cooled toroom temperature and poured in 100 ml of methanol. The resultingdeposited solid matter was separated by filtration and washed withmethanol, water and then acetone. Then, the solid matter was washed withacetone and hexane in this order using a Soxhlet extractor. Next, afterthe solid matter was dissolved in chloroform, and resulting chloroformsolution was passed through celite (produced by Nacalai Tesque Inc.) andsubsequently through a silica-gel column (eluent: chloroform), thesolvent was distilled off under reduced pressure. The resulting solidmatter was dissolved in chloroform again, and then re-precipitated inmethanol to obtain a compound B-4 (73 mg). The compound B-4 had a weightaverage molecular weight of 21000 and a number average molecular weightof 11000. Further, the compound B-4 had an optical absorption edgewavelength of 785 nm, a bandgap (Eg) of 1.58 eV, and the highestoccupied molecular orbital (HOMO) level of −4.92 eV.

Example 1

The above-mentioned compound (A-1) (1 mg) and PC₇₀BM (1 mg) (produced bySolenne BV) were added to 0.20 ml of a chloroform solution containing1,8-diiodooctane (produced by Wako Pure Chemical Industries, Ltd.) at arate of 3% by volume, and a container containing the chloroform solutionwas irradiated with ultrasonic waves for 30 minutes in a ultrasoniccleaning machine (US-2 (trade name) manufactured by Iuchi Seieido Co.,Ltd., output: 120 W) to obtain a solution A (a weight ratio between adonor and an acceptor is 1:1). Further, the compound (A-1) (1 mg) andPC₇₀BM (1.5 mg) (produced by Solenne BV) were put into a sample bottlecontaining 0.25 ml of a chloroform solution (volume concentration of 3%)of 1,8-diiodooctane (produced by Wako Pure Chemical Industries, Ltd.),and this was irradiated with ultrasonic waves for 30 minutes in aultrasonic cleaning machine (US-2 (trade name) manufactured by IuchiSeieido Co., Ltd., output: 120 W) to obtain a solution B (a weight ratiobetween a donor and an acceptor is 1:1.5).

A glass substrate on which an ITO transparent conductive layer servingas a positive electrode was deposited at a thickness of 125 nm by asputtering method was cut into a size of 38 mm×46 mm, and the ITO layerwas then patterned into a rectangular shape of 38 mm×13 mm by aphotolithography method. The resulting substrate was cleaned withultrasonic waves for 10 minutes in an alkali cleaning solution(“Semicoclean” EL56 (trade name), produced by Furuuchi ChemicalCorporation), and then washed with ultrapure water.

After this substrate was subjected to a UV/ozone treatment for 30minutes, an aqueous PEDOT:PSS solution (PEDOT 0.8% by weight, PPS 0.5%by weight) to be used to form a hole transporting layer was applied ontothe substrate by a spin coating method so as to form a film with athickness of 60 nm. After being heated and dried at 200° C. for 5minutes by using a hot plate, the above-mentioned solution A or solutionB was added dropwise to the PEDOT:PPS layer and an organic semiconductorlayer having a film thickness of 130 nm was formed by a spin coatingmethod. Thereafter, the substrate with the organic semiconductor layerformed thereon and a mask for a negative electrode were placed in avacuum vapor deposition apparatus, and the apparatus was again evacuateduntil the degree of vacuum inside the apparatus reached 1×10⁻³ Pa orless and a lithium fluoride layer was vapor-deposited with a thicknessof 0.1 nm by a resistive heating method. Thereafter, an aluminum layerserving as a negative electrode was vapor-deposited with a thickness of80 nm. Thus, a photovoltaic device, in which an area of an intersectionportion of the stripe-shaped ITO layer and the stripe-shaped aluminumlayer is 2 mm×2 mm, was prepared.

The positive and negative electrodes of the photovoltaic device thusprepared were connected to a 2400 series SourceMeter manufactured by TFFCorporation Keithley Instruments, and the device was irradiated withpseudo-solar light (OTENTO-SUNIII manufactured by Bunkoukeiki Co., Ltd.,spectral-shape: AM 1.5, Intensity: 100 mW/cm²) from the ITO layer sidein the atmosphere, and the current value was measured, with the appliedvoltage being varied from −1 V to +2 V. Results of the measurement areshown in FIG. 5. In the photovoltaic device using the solution A (theweight ratio between a donor and an acceptor was 1:1), the short-circuitcurrent density (value of the current density when the applied voltageis 0 V) was 15.99 A/cm², the open circuit voltage (value of the appliedvoltage when the current density is 0) was 0.76 V, and the fill factor(FF) was 0.69, and the photoelectric conversion efficiency calculatedbased upon these values was 8.39%. The voltage-current density curve inthis is shown in FIG. 5. FIG. 5 is a graph with a voltage on thehorizontal-axis and an current density on the vertical-axis. Further, inthe photovoltaic device using the solution B (the weight ratio between adonor and an acceptor was 1:1.5), the short-circuit current density was13.56 A/cm², the open circuit voltage was 0.76 V, and the fill factor(FF) was 0.68, and the photoelectric conversion efficiency calculatedbased on these values was 7.01%.

The fill factor and the photoelectric conversion efficiency werecalculated from the following expression:Fill factor=IVmax (mA·V/cm²)/(Short-circuit current density(mA/cm²)×Opencircuit voltage (V))wherein, IVmax corresponds to a value of product of the current densityand the applied voltage at a point where the product of the currentdensity and the applied voltage becomes the largest with the appliedvoltage between 0 V and the open circuit voltage value. Photoelectricconversion efficiency=[(Short-circuit current density (mA/cm²)×Opencircuit voltage (V)×Fill factor)/Intensity of pseudo-solar light (100mW/cm²)]×100(%) In the following examples and comparative examples, allthe fill factor and photoelectric conversion efficiency were calculatedfrom the above-mentioned expression.

Example 2

A photovoltaic device was prepared, and the current-voltagecharacteristics were measured in the same manner as in Example 1 exceptfor using the above-mentioned compound A-2 in place of the compound A-1.In the characteristics of the device using the solution in which theweight ratio between a donor and an acceptor was 1:1, the short-circuitcurrent density was 13.71 mA/cm², the open circuit voltage was 0.81 V,and the fill factor (FF) was 0.65, and the photoelectric conversionefficiency calculated based on these values was 7.22%. Further, in thecharacteristics of the device using the solution in which the weightratio between a donor and an acceptor was 1:1.5, the short-circuitcurrent density was 14.04 mA/cm², the open circuit voltage was 0.81 V,and the fill factor (FF) was 0.66, and the photoelectric conversionefficiency calculated based on these values was 7.51%.

Example 3

A photovoltaic device was prepared, and the current-voltagecharacteristics were measured in the same manner as in Example 1 exceptfor using the above-mentioned compound A-3 in place of the compound A-1.In the characteristics of the device using the solution in which theweight ratio between a donor and an acceptor was 1:1, the short-circuitcurrent density was 13.71 mA/cm², the open circuit voltage was 0.73 V,and the fill factor (FF) was 0.68, and the photoelectric conversionefficiency calculated based on these values was 6.81%. Further, in thecharacteristics of the device using the solution in which the weightratio between a donor and an acceptor was 1:1.5, the short-circuitcurrent density was 13.94 mA/cm², the open circuit voltage was 0.73 V,and the fill factor (FF) was 0.68, and the photoelectric conversionefficiency calculated based on these values was 6.92%.

Example 4

A photovoltaic device was prepared, and the current-voltagecharacteristics were measured in the same manner as in Example 1 exceptfor using the above-mentioned compound A-4 in place of the compound A-1.In the characteristics of the device using the solution in which theweight ratio between a donor and an acceptor was 1:1, the short-circuitcurrent density was 13.75 mA/cm², the open circuit voltage was 0.76 V,and the fill factor (FF) was 0.68, and the photoelectric conversionefficiency calculated based on these values was 7.11%. Further, in thecharacteristics of the device using the solution in which the weightratio between a donor and an acceptor was 1:1.5, the short-circuitcurrent density was 13.42 mA/cm², the open circuit voltage was 0.76 V,and the fill factor (FF) was 0.67, and the photoelectric conversionefficiency calculated based on these values was 6.83%.

Comparative Example 1

A photovoltaic device was prepared, and the current-voltagecharacteristics were measured in the same manner as in Example 1 exceptfor using the above-mentioned compound B-1 in place of the compound A-1.In the characteristics of the device using the solution in which theweight ratio between a donor and an acceptor was 1:1, the short-circuitcurrent density was 11.20 mA/cm², the open circuit voltage was 0.74 V,and the fill factor (FF) was 0.59, and the photoelectric conversionefficiency calculated based on these values was 4.89%. Further, in thecharacteristics of the device using the solution in which the weightratio between a donor and an acceptor was 1:1.5, the short-circuitcurrent density was 12.74 mA/cm², the open circuit voltage was 0.74 V,and the fill factor (FF) was 0.66, and the photoelectric conversionefficiency calculated based on these values was 6.39%.

Comparative Example 2

A photovoltaic device was prepared, and the current-voltagecharacteristics were measured in the same manner as in Example 1 exceptfor using the above-mentioned compound B-2 in place of the compound A-1.In the characteristics of the device using the solution in which theweight ratio between a donor and an acceptor was 1:1, the short-circuitcurrent density was 11.44 mA/cm², the open circuit voltage was 0.74 V,and the fill factor (FF) was 0.62, and the photoelectric conversionefficiency calculated based on these values was 5.25%. Further, in thecharacteristics of the device using the solution in which the weightratio between a donor and an acceptor was 1:1.5, the short-circuitcurrent density was 11.22 mA/cm², the open circuit voltage was 0.74 V,and the fill factor (FF) was 0.60, and the photoelectric conversionefficiency calculated based on these values was 4.98%.

Comparative Example 3

A photovoltaic device was prepared, and the current-voltagecharacteristics were measured in the same manner as in Example 1 exceptfor using the above-mentioned compound B-3 in place of the compound A-1.In the characteristics of the device using the solution in which theweight ratio between a donor and an acceptor was 1:1, the short-circuitcurrent density was 11.19 mA/cm², the open circuit voltage was 0.68 V,and the fill factor (FF) was 0.57, and the photoelectric conversionefficiency calculated based on these values was 4.34%. Further, in thecharacteristics of the device using the solution in which the weightratio between a donor and an acceptor was 1:1.5, the short-circuitcurrent density was 12.56 mA/cm², the open circuit voltage was 0.68 V,and the fill factor (FF) was 0.55, and the photoelectric conversionefficiency calculated based on these values was 4.70%.

Comparative Example 4

A photovoltaic device was prepared, and the current-voltagecharacteristics were measured in the same manner as in Example 1 exceptfor using the above-mentioned compound B-4 in place of the compound A-1.In the characteristics of the device using the solution in which theweight ratio between a donor and an acceptor was 1:1, the short-circuitcurrent density was 13.51 mA/cm², the open circuit voltage was 0.74 V,and the fill factor (FF) was 0.59, and the photoelectric conversionefficiency calculated based on these values was 5.90%. Further, in thecharacteristics of the device using the solution in which the weightratio between a donor and an acceptor was 1:1.5, the short-circuitcurrent density was 15.02 mA/cm², the open circuit voltage was 0.74 V,and the fill factor (FF) was 0.61, and the photoelectric conversionefficiency calculated based on these values was 6.78%.

TABLE 1 Electron Short-Circuit Open Donating Ratio between ElectronElectron Current Circuit Photoelectric Organic Donor and TransportingExtraction Negative Density Voltage Fill Conversion Material AcceptorLayer Layer Electrode (mA/cm²) (V) Factor Efficiency (%) Example 1 A-11:1   — LiF Al 15.99 0.76 0.69 8.39 1:1.5 — LiF Al 13.56 0.76 0.68 7.01Example 2 A-2 1:1   — LiF Al 13.71 0.81 0.65 7.22 1:1.5 — LiF Al 14.040.81 0.66 7.51 Example 3 A-3 1:1   — LiF Al 13.71 0.73 0.68 6.81 1:1.5 —LiF Al 13.94 0.73 0.68 6.92 Example 4 A-4 1:1   — LiF Al 13.75 0.76 0.687.11 1:1.5 — LiF Al 13.42 0.76 0.67 6.83 Comparative B-1 1:1   — LiF Al11.20 0.74 0.59 4.89 Example 1 1:1.5 — LiF Al 12.74 0.74 0.66 6.39Comparative B-2 1:1   — LiF Al 11.44 0.74 0.62 5.25 Example 2 1:1.5 —LiF Al 11.22 0.74 0.60 4.98 Comparative B-3 1:1   — LiF Al 11.19 0.680.57 4.34 Example 3 1:1.5 — LiF Al 12.56 0.68 0.55 4.70 Comparative B-41:1   — LiF Al 13.51 0.74 0.59 5.90 Example 4 1:1.5 — LiF Al 15.02 0.740.61 6.78 Example 5 A-1 1:1.2 — LiF Al 14.08 0.77 0.69 7.52 Example 6A-1 1:1.2 ZnO — Al 14.95 0.77 0.66 7.63 Example 7 A-1 1:1.2 E-1 — Al14.89 0.79 0.69 8.13 Example 8 A-1 1:1.2 E-2 — Al 14.63 0.78 0.72 8.17Example 9 A-1 1:1.2 E-2 — Ag 15.26 0.77 0.70 8.20 Example 10 A-1 1:1.2E-2 LiF Ag 15.36 0.78 0.71 8.50 Example 11 A-1 1:1.2 E-3 — Al 14.55 0.780.69 7.87 Example 12 A-1 1:1.2 E-4 — Al 14.17 0.76 0.72 7.79 Example 13A-1 1:1.2 E-5 LiF Al 14.61 0.78 0.70 7.93 Example 14 A-1 1:1.2 E-5 LiFAg 14.67 0.77 0.70 7.93 Example 15 A-1 1:1.2 E-6 LiF Al 14.96 0.78 0.708.15

As is evident from Table 1, the photovoltaic devices (Examples 1 to 4)prepared from the electron donating organic material using theconjugated polymer having a structure represented by formula (1)exhibited higher photoelectric conversion efficiency than otherphotovoltaic devices (Comparative Examples 1 to 4) prepared in the sameconditions.

Example 5

The compound (A-1) (0.9 mg) and PC₇₀BM (1.1 mg) (produced by Solenne BV)were added to 0.20 ml of a chloroform solution containing1,8-diiodooctane (produced by Wako Pure Chemical Industries, Ltd.) at arate of 2% by volume, and a container containing the chloroform solutionwas irradiated with ultrasonic waves for 30 minutes in a ultrasoniccleaning machine (US-2 (trade name) manufactured by Iuchi Seieido Co.,Ltd., output: 120 W) to obtain a solution C (a weight ratio between adonor and an acceptor is 1:1.2).

A photovoltaic device having an area of 5 mm×5 mm was prepared, and thecurrent-voltage characteristics were measured in the same manner as inExample 1 except for vapor-depositing a lithium fluoride layer at athickness of 0.5 nm. The short-circuit current density was 14.08 mA/cm²,the open circuit voltage was 0.77 V, and the fill factor (FF) was 0.69,and the photoelectric conversion efficiency calculated based on thesevalues was 7.52%.

Example 6

After the above-mentioned cleaned substrate was subjected to a UV/ozonetreatment for 30 minutes, a solution which was formed by dissolving zincacetate dihydrate (20 mg) (produced by Wako Pure Chemical Industries,Ltd.) in a mixed solvent (1 ml) of ethanol and water (100:1) was appliedonto the substrate by spin coating at 1500 rpm, and heated at 200° C.for 1 hour on a hot plate. After heating, the resulting coated substratewas cooled to room temperature, and a solution formed by dissolving 0.5mg of sodium myristate (produced by Tokyo Chemical Industry Co., Ltd.)in 1 ml of ethanol was applied onto the coated substrate by spin coatingat 1000 rpm, and the solution was heated at 110° C. for 10 minutes on ahot plate to form an electron transporting layer. The above-mentionedsolution C was added dropwise to the electron transporting layer, and anorganic semiconductor layer having a thickness of 130 nm was formed by aspin coating method. Thereafter, the substrate with the organicsemiconductor layer formed thereon and a mask for a negative electrodewere placed in a vacuum vapor deposition apparatus, and the apparatuswas again evacuated until the degree of vacuum inside the apparatusreached 1×10⁻³ Pa or less and a molybdenum oxide layer wasvapor-deposited with a thickness of 10 nm by a resistive heating method.Thereafter, an aluminum layer serving as a negative electrode wasvapor-deposited at a thickness of 80 nm. As described above, aphotovoltaic device, in which an area of an intersection portion of thestripe-shaped ITO layer and the stripe-shaped aluminum layer is 5 mm×5mm, was prepared, and the current-voltage characteristics were measured.The short-circuit current density was 14.95 mA/cm², the open circuitvoltage was 0.77 V, and the fill factor (FF) was 0.66, and thephotoelectric conversion efficiency calculated based on these values was7.63%.

Synthesis Example 9

A compound E-1 was synthesized by the following method.1,10-phenanthroline (9.64 g) was reacted with phenyl lithium (100 ml)(1.07 M cyclohexane/ether solution) at 0° C. for 1.5 hours in toluene(250 ml) and treated by a conventional method. The resulting product wasreacted with manganese dioxide (93.0 g) at room temperature for 56 hoursin dichloromethane (300 ml) and treated by a conventional method toobtain 9.44 g of 2-phenyl-1,10-phenanthroline. To 25 ml of a THFsolution of 1,3-dibromobenzene (0.34 ml) was added an t-butyl lithium(1.53 M pentane solution) (7.35 mL) at −78° C., and the resultingmixture was stirred for 1 hour, and then its temperature was raised to0° C. The resulting solution was added to 85 ml of a THF solution of theobtained 2-phenyl-1,10-phenanthroline (1.44 g), and the resultingmixture was stirred at room temperature for 20 hours, and treated by aconventional method. The resulting product was reacted with manganesedioxide (8.50 g) at room temperature for 23 hours in dichloromethane (85ml) and treated by a conventional method to obtain 1.08 g of a compoundE-1.

Synthesis Example 10

A compound E-2 was synthesized by the following method.1,3-diacetylbenzene (5.0 g) and 8-amino-7-quinolinecarbaldehyde (11.1 g)were dissolved in ethanol (180 ml) in a nitrogen atmosphere, and to thiswas added dropwise an ethanol solution (130 ml) of potassium hydroxide(8.52 g) while stirring the resulting mixture. The resulting mixture wasrefluxed for 11 hours, and then the resulting product was treated by aconventional method to obtain 11.0 g of a compound E-2.

Synthesis Example 11

A compound E-6 was synthesized by the following method. 2,2′-biphenol(11 g) was dissolved in dichloromethane (100 ml) and pyridine (23.8 ml)in a nitrogen atmosphere, and to this was added dropwisetrifluoromethane sulfonic acid anhydride (35 g) at 0° C. The resultingmixture was stirred at 0° C. for 2 hours and then treated by aconventional method to obtain 26.3 g of2,2′-bis(trifluoromethanesulfonyloxyphenyl)biphenyl. To acetonitrile(100 ml) were added 2,2′-bis(trifluoromethanesulfonyloxyphenyl)biphenyl(10 g), 4-acetylphenylboronic acid (10.92 g), cesium fluoride (16.78 g),and tetrakis(triphenyl phosphine)palladium (1.28 g) in a nitrogenatmosphere, the resulting mixture was refluxed for two days and treatedby a conventional method to obtain 5.59 g of2,2′-di(4-acetylphenyl)biphenyl. A compound E-6 (4.9 g) was preparedfrom this 2,2′-di(4-acetylphenyl)biphenyl and8-amino-7-quinolinecarbaldehyde (2.78 g) by the same reaction treatmentas in Synthesis Example 10.

In addition, the E-1, E-2 and E-6 were used after purification bysublimation.

Example 7

A photovoltaic device having an area of 5 mm×5 mm was prepared, and thecurrent-voltage characteristics were measured in the same manner as inExample 5 except for using the compound E-1 (5 nm) in place of thelithium fluoride (0.1 nm). The short-circuit current density was 14.89mA/cm², the open circuit voltage was 0.79 V, and the fill factor (FF)was 0.69, and the photoelectric conversion efficiency calculated basedon these values was 8.13%.

Example 8

A photovoltaic device having an area of 5 mm×5 mm was prepared, and thecurrent-voltage characteristics were measured in the same manner as inExample 7 except for using the compound E-2 in place of the compoundE-1. The short-circuit current density was 14.63 mA/cm², the opencircuit voltage was 0.78 V, and the fill factor (FF) was 0.72, and thephotoelectric conversion efficiency calculated based on these values was8.17%.

Example 9

A photovoltaic device having an area of 5 mm×5 mm was prepared, and thecurrent-voltage characteristics were measured in the same manner as inExample 7 except for using the compound E-2 in place of the compound E-1and using silver in place of aluminum. The short-circuit current densitywas 15.26 mA/cm², the open circuit voltage was 0.77 V, and the fillfactor (FF) was 0.70, and the photoelectric conversion efficiencycalculated based on these values was 8.20%.

Example 10

A photovoltaic device having an area of 5 mm×5 mm was prepared, and thecurrent-voltage characteristics were measured in the same manner as inExample 7 except for using the compound E-2 (5 nm)/LiF (0.5 nm) in placeof the compound E-1 (5 nm) and using silver in place of aluminum. Theshort-circuit current density was 15.36 mA/cm², the open circuit voltagewas 0.78 V, and the fill factor (FF) was 0.71, and the photoelectricconversion efficiency calculated based on these values was 8.50%.

Example 11

A photovoltaic device having an area of 5 mm×5 mm was prepared, and thecurrent-voltage characteristics were measured in the same manner as inExample 7 except for using the compound E-3(8-hydroxyquinolinolato-lithium (Liq) produced by LuminescenceTechnology Corporation) (2.5 nm) in place of the compound E-1 (5 nm).The short-circuit current density was 14.55 mA/cm², the open circuitvoltage was 0.78 V, and the fill factor (FF) was 0.69, and thephotoelectric conversion efficiency calculated based on these values was7.87%.

Example 12

A photovoltaic device having an area of 5 mm×5 mm was prepared, and thecurrent-voltage characteristics were measured in the same manner as inExample 7 except for using the compound E-4 (Phenyl-dipyrenylphosphineoxide(PoPy2) produced by Luminescence Technology Corporation) (2.5 nm)in place of the compound E-1 (5 nm). The short-circuit current densitywas 14.17 mA/cm², the open circuit voltage was 0.76 V, and the fillfactor (FF) was 0.72, and the photoelectric conversion efficiencycalculated based on these values was 7.79%.

Example 13

A photovoltaic device having an area of 5 mm×5 mm was prepared, and thecurrent-voltage characteristics were measured in the same manner as inExample 7 except for using the compound E-5(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) produced byLuminescence Technology Corporation) (5 nm)/LiF (0.5 nm) in place of thecompound E-1 (5 nm). The short-circuit current density was 14.61 mA/cm²,the open circuit voltage was 0.78 V, and the fill factor (FF) was 0.70,and the photoelectric conversion efficiency calculated based on thesevalues was 7.93%.

Example 14

A photovoltaic device having an area of 5 mm×5 mm was prepared, and thecurrent-voltage characteristics were measured in the same manner as inExample 7 except for using the compound E-5 (5 nm)/LiF (0.5 nm) in placeof the compound E-1 (5 nm) and using silver in place of aluminum. Theshort-circuit current density was 14.67 mA/cm², the open circuit voltagewas 0.77 V, and the fill factor (FF) was 0.70, and the photoelectricconversion efficiency calculated based on these values was 7.93%.

Example 15

A photovoltaic device having an area of 5 mm×5 mm was prepared, and thecurrent-voltage characteristics were measured in the same manner as inExample 7 except for using the compound E-6 (5 nm)/LiF (0.5 nm) in placeof the compound E-1 (5 nm). The short-circuit current density was 14.96mA/cm², the open circuit voltage was 0.78 V, and the fill factor (FF)was 0.70, and the photoelectric conversion efficiency calculated basedon these values was 8.15%.

As is evident from Table 1, the photovoltaic devices (Examples 6 to 15)having the electron transporting layer between the negative electrodeand the layer of the material for a photovoltaic device exhibited higherphotoelectric conversion efficiency than the photovoltaic device(Example 5) not having the electron transporting layer. Moreover, whenthe phenanthroline derivative was used for the electron transportinglayer material, (Examples 7 to 10 and 13 to 15) the product exhibitedhigher photoelectric conversion efficiency than when other materialswere used for the electron transporting layer (Examples 11 and 12), andwhen the phenanthroline dimer compounds were used for the electrontransporting layer (Examples 7 to 10 and 15), the product exhibitedparticularly high photoelectric conversion efficiency.

The invention claimed is:
 1. A conjugated polymer having a structurerepresented by formula (1):

wherein R¹ represents an alkoxycarbonyl group in which an alkyl grouppart is a straight chain alkyl group or an alkanoyl group in which analkyl group part is a straight chain alkyl group, and the groups may besubstituted as long as they maintain a straight chain structure; each ofR²s which may be the same or different represents an optionallysubstituted heteroaryl group; X represents a hydrogen atom or a halogenatom, n is a polymerization degree and represents an integer of 2 ormore and 1000 or less.
 2. The conjugated polymer according to claim 1,wherein X is fluorine.
 3. An electron donating organic materialcomprising the conjugated polymer according to claim
 1. 4. A materialfor a photovoltaic device containing the electron donating organicmaterial according to claim 3 and an electron accepting organicmaterial.
 5. The material according to claim 4, wherein the electronaccepting organic material is a fullerene compound.
 6. The materialaccording to claim 5, wherein the fullerene compound contains a C₇₀derivative.
 7. A photovoltaic device comprising at least a positiveelectrode and a negative electrode, wherein the photovoltaic device hasan organic semiconductor layer containing the material for thephotovoltaic device according to claim 4 between the positive electrodeand the negative electrode.
 8. The photovoltaic device according toclaim 7, further comprising an electron transporting layer between thenegative electrode and the organic semiconductor layer containing thematerial for the photovoltaic device.
 9. The photovoltaic deviceaccording to claim 8, wherein the electron transporting layer contains aphenanthroline derivative.
 10. An electron donating organic materialcomprising the conjugated polymer according to claim
 2. 11. A materialfor a photovoltaic device containing the electron donating organicmaterial according to claim 10 and an electron accepting organicmaterial.
 12. A photovoltaic device comprising at least a positiveelectrode and a negative electrode, wherein the photovoltaic device hasan organic semiconductor layer containing the material for thephotovoltaic device according to claim 5 between the positive electrodeand the negative electrode.
 13. A photovoltaic device comprising atleast a positive electrode and a negative electrode, wherein thephotovoltaic device has an organic semiconductor layer containing thematerial for the photovoltaic device according to claim 6 between thepositive electrode and the negative electrode.